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Re: question about strange results from LPR filter

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  • Don Goldman
    Peter, the scan that came with the Baadar showed very sharp cutoffs at 400 and 700 nm with the UV and NIR blocked. I find it hard to accept your premise about
    Message 1 of 18 , Apr 1, 2004
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      Peter, the scan that came with the Baadar showed very sharp cutoffs
      at 400 and 700 nm with the UV and NIR blocked.

      I find it hard to accept your premise about a filter that blocks up
      to 430 nm. That does not leave much in the blue spectral region,
      although it will certainly remove blue halos in refractors, as does
      the minus violet filter from Lumicon.

      Don Goldman
      www.astrodon.com



      --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...> wrote:
      > The Baader UV/NIR filter does block NIR, and may be the best filter
      > available for the purpose. But I remain confused how it can be
      called
      > a UV blocker when it has appreciable transmission down to nearly
      > 300nm. At that point atmospheric ozone is the more important
      blocker.
      >
      > I'm still waiting for a properly designed UV/NIR blocker suitable
      for
      > APO refractors, tranmission range of 450-850nm where they are mostly
      > still diffraction limited. Everything presently cuts off at 700nm
      > (too early, wasting light) and transmits down to below 400nm (much
      too
      > far).
      >
      > Peter
      >
      > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
      <donclearview@y...>
      > wrote:
      > > Alex,
      > >
      > > The Meade, and I suspect, Celestron LPS filter let near-infrared
      > > light pass to the web cam. The Meade LPS blocks UV. Don't have
      any
      > > data on the Celestron. The chromatic aberration you're seeing is
      > > likely related to this. I saw it in my own web cam. The more
      > > expensive Hutech/IDAS LPS blocks UV and NIR but may not provide
      good
      > > overall color balance for your camera. I think the best solution
      is
      > > to buy the new Baadar UV/NIR cutoff filter for $42. It solves
      this
      > > problem. I bought mine from Alpine Astronomical, but I think
      > > Adirondack now sells them, too.
      > >
      > > Don Goldman
      > > www.astrodon.com
      > >
      > >
      > > --- In ccd-newastro@yahoogroups.com, "ianderca" <ianderca@y...>
      wrote:
      > > > I have just bought a celestron LPR filter, and I notice a
      > > remarkable
      > > > cromatic aberration from my photo with webcam but in visual
      too:
      > > the
      > > > filter produce a red and blu abberration on the opposite side
      of a
      > > > star for example, similar but more accentuated than cromatic
      > > > aberration from stars at low level hight. This is normal? If
      yes ,
      > > > do you mean that you can use this filter only for visual
      > > observation
      > > > of faint object?
      > > >
      > > > please, if someone have any experience about using it I would
      > > > appreciate any information. I wonder if my filter is bad.
      > > >
      > > > best regards
      > > > Alex
    • erdmanpe
      The curve that I was referring to was the one on the Adirondack web site. There, below the sharp cut-off at 400nm, is another peak extending down to nearly
      Message 2 of 18 , Apr 1, 2004
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        The curve that I was referring to was the one on the Adirondack web
        site. There, below the sharp cut-off at 400nm, is another peak
        extending down to nearly 300nm. Did the curve that came with your
        filter extend the data down to 300nm? Certainly moving the cut-off to
        430nm eats into the blue flux, but unfortunately that seems to be
        where any APOs that I've seen data on start to become diffraction
        limited (hence the blue halos otherwise).

        Peter

        --- In ccd-newastro@yahoogroups.com, "Don Goldman" <donclearview@y...>
        wrote:
        > Peter, the scan that came with the Baadar showed very sharp cutoffs
        > at 400 and 700 nm with the UV and NIR blocked.
        >
        > I find it hard to accept your premise about a filter that blocks up
        > to 430 nm. That does not leave much in the blue spectral region,
        > although it will certainly remove blue halos in refractors, as does
        > the minus violet filter from Lumicon.
        >
        > Don Goldman
        > www.astrodon.com
        >
        >
        >
        > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...> wrote:
        > > The Baader UV/NIR filter does block NIR, and may be the best filter
        > > available for the purpose. But I remain confused how it can be
        > called
        > > a UV blocker when it has appreciable transmission down to nearly
        > > 300nm. At that point atmospheric ozone is the more important
        > blocker.
        > >
        > > I'm still waiting for a properly designed UV/NIR blocker suitable
        > for
        > > APO refractors, tranmission range of 450-850nm where they are mostly
        > > still diffraction limited. Everything presently cuts off at 700nm
        > > (too early, wasting light) and transmits down to below 400nm (much
        > too
        > > far).
        > >
        > > Peter
        > >
        > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
        > <donclearview@y...>
        > > wrote:
        > > > Alex,
        > > >
        > > > The Meade, and I suspect, Celestron LPS filter let near-infrared
        > > > light pass to the web cam. The Meade LPS blocks UV. Don't have
        > any
        > > > data on the Celestron. The chromatic aberration you're seeing is
        > > > likely related to this. I saw it in my own web cam. The more
        > > > expensive Hutech/IDAS LPS blocks UV and NIR but may not provide
        > good
        > > > overall color balance for your camera. I think the best solution
        > is
        > > > to buy the new Baadar UV/NIR cutoff filter for $42. It solves
        > this
        > > > problem. I bought mine from Alpine Astronomical, but I think
        > > > Adirondack now sells them, too.
        > > >
        > > > Don Goldman
        > > > www.astrodon.com
        > > >
        > > >
        > > > --- In ccd-newastro@yahoogroups.com, "ianderca" <ianderca@y...>
        > wrote:
        > > > > I have just bought a celestron LPR filter, and I notice a
        > > > remarkable
        > > > > cromatic aberration from my photo with webcam but in visual
        > too:
        > > > the
        > > > > filter produce a red and blu abberration on the opposite side
        > of a
        > > > > star for example, similar but more accentuated than cromatic
        > > > > aberration from stars at low level hight. This is normal? If
        > yes ,
        > > > > do you mean that you can use this filter only for visual
        > > > observation
        > > > > of faint object?
        > > > >
        > > > > please, if someone have any experience about using it I would
        > > > > appreciate any information. I wonder if my filter is bad.
        > > > >
        > > > > best regards
        > > > > Alex
      • Don Goldman
        Peter, just spectrally measured the Baader filter here at work. The small peaks that you see posted at Adirondack below 400 nm are there. They amount to only
        Message 3 of 18 , Apr 1, 2004
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          Peter, just spectrally measured the Baader filter here at work. The
          small peaks that you see posted at Adirondack below 400 nm are
          there. They amount to only about 4% of a typical blue filter
          transmission, and about 1.5% of the Red+Green+Blue. Since the CCD
          QE drops off so strongly below about 420 nm, these peaks will not
          have much of an effect. I think this is an excellent low-cost filter
          for the web-cams.

          Don Goldman
          www.astrodon.com


          --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...> wrote:
          > The curve that I was referring to was the one on the Adirondack web
          > site. There, below the sharp cut-off at 400nm, is another peak
          > extending down to nearly 300nm. Did the curve that came with your
          > filter extend the data down to 300nm? Certainly moving the cut-off
          to
          > 430nm eats into the blue flux, but unfortunately that seems to be
          > where any APOs that I've seen data on start to become diffraction
          > limited (hence the blue halos otherwise).
          >
          > Peter
          >
          > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
          <donclearview@y...>
          > wrote:
          > > Peter, the scan that came with the Baadar showed very sharp
          cutoffs
          > > at 400 and 700 nm with the UV and NIR blocked.
          > >
          > > I find it hard to accept your premise about a filter that blocks
          up
          > > to 430 nm. That does not leave much in the blue spectral region,
          > > although it will certainly remove blue halos in refractors, as
          does
          > > the minus violet filter from Lumicon.
          > >
          > > Don Goldman
          > > www.astrodon.com
          > >
          > >
          > >
          > > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...>
          wrote:
          > > > The Baader UV/NIR filter does block NIR, and may be the best
          filter
          > > > available for the purpose. But I remain confused how it can be
          > > called
          > > > a UV blocker when it has appreciable transmission down to nearly
          > > > 300nm. At that point atmospheric ozone is the more important
          > > blocker.
          > > >
          > > > I'm still waiting for a properly designed UV/NIR blocker
          suitable
          > > for
          > > > APO refractors, tranmission range of 450-850nm where they are
          mostly
          > > > still diffraction limited. Everything presently cuts off at
          700nm
          > > > (too early, wasting light) and transmits down to below 400nm
          (much
          > > too
          > > > far).
          > > >
          > > > Peter
          > > >
          > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
          > > <donclearview@y...>
          > > > wrote:
          > > > > Alex,
          > > > >
          > > > > The Meade, and I suspect, Celestron LPS filter let near-
          infrared
          > > > > light pass to the web cam. The Meade LPS blocks UV. Don't
          have
          > > any
          > > > > data on the Celestron. The chromatic aberration you're
          seeing is
          > > > > likely related to this. I saw it in my own web cam. The
          more
          > > > > expensive Hutech/IDAS LPS blocks UV and NIR but may not
          provide
          > > good
          > > > > overall color balance for your camera. I think the best
          solution
          > > is
          > > > > to buy the new Baadar UV/NIR cutoff filter for $42. It
          solves
          > > this
          > > > > problem. I bought mine from Alpine Astronomical, but I think
          > > > > Adirondack now sells them, too.
          > > > >
          > > > > Don Goldman
          > > > > www.astrodon.com
          > > > >
          > > > >
          > > > > --- In ccd-newastro@yahoogroups.com, "ianderca"
          <ianderca@y...>
          > > wrote:
          > > > > > I have just bought a celestron LPR filter, and I notice a
          > > > > remarkable
          > > > > > cromatic aberration from my photo with webcam but in visual
          > > too:
          > > > > the
          > > > > > filter produce a red and blu abberration on the opposite
          side
          > > of a
          > > > > > star for example, similar but more accentuated than
          cromatic
          > > > > > aberration from stars at low level hight. This is normal?
          If
          > > yes ,
          > > > > > do you mean that you can use this filter only for visual
          > > > > observation
          > > > > > of faint object?
          > > > > >
          > > > > > please, if someone have any experience about using it I
          would
          > > > > > appreciate any information. I wonder if my filter is bad.
          > > > > >
          > > > > > best regards
          > > > > > Alex
        • erdmanpe
          That would be good news. Peter
          Message 4 of 18 , Apr 1, 2004
          • 0 Attachment
            That would be good news.
            Peter

            --- In ccd-newastro@yahoogroups.com, "Don Goldman" <donclearview@y...>
            wrote:
            > Peter, just spectrally measured the Baader filter here at work. The
            > small peaks that you see posted at Adirondack below 400 nm are
            > there. They amount to only about 4% of a typical blue filter
            > transmission, and about 1.5% of the Red+Green+Blue. Since the CCD
            > QE drops off so strongly below about 420 nm, these peaks will not
            > have much of an effect. I think this is an excellent low-cost filter
            > for the web-cams.
            >
            > Don Goldman
            > www.astrodon.com
            >
            >
            > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...> wrote:
            > > The curve that I was referring to was the one on the Adirondack web
            > > site. There, below the sharp cut-off at 400nm, is another peak
            > > extending down to nearly 300nm. Did the curve that came with your
            > > filter extend the data down to 300nm? Certainly moving the cut-off
            > to
            > > 430nm eats into the blue flux, but unfortunately that seems to be
            > > where any APOs that I've seen data on start to become diffraction
            > > limited (hence the blue halos otherwise).
            > >
            > > Peter
            > >
            > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
            > <donclearview@y...>
            > > wrote:
            > > > Peter, the scan that came with the Baadar showed very sharp
            > cutoffs
            > > > at 400 and 700 nm with the UV and NIR blocked.
            > > >
            > > > I find it hard to accept your premise about a filter that blocks
            > up
            > > > to 430 nm. That does not leave much in the blue spectral region,
            > > > although it will certainly remove blue halos in refractors, as
            > does
            > > > the minus violet filter from Lumicon.
            > > >
            > > > Don Goldman
            > > > www.astrodon.com
            > > >
            > > >
            > > >
            > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...>
            > wrote:
            > > > > The Baader UV/NIR filter does block NIR, and may be the best
            > filter
            > > > > available for the purpose. But I remain confused how it can be
            > > > called
            > > > > a UV blocker when it has appreciable transmission down to nearly
            > > > > 300nm. At that point atmospheric ozone is the more important
            > > > blocker.
            > > > >
            > > > > I'm still waiting for a properly designed UV/NIR blocker
            > suitable
            > > > for
            > > > > APO refractors, tranmission range of 450-850nm where they are
            > mostly
            > > > > still diffraction limited. Everything presently cuts off at
            > 700nm
            > > > > (too early, wasting light) and transmits down to below 400nm
            > (much
            > > > too
            > > > > far).
            > > > >
            > > > > Peter
            > > > >
            > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
            > > > <donclearview@y...>
            > > > > wrote:
            > > > > > Alex,
            > > > > >
            > > > > > The Meade, and I suspect, Celestron LPS filter let near-
            > infrared
            > > > > > light pass to the web cam. The Meade LPS blocks UV. Don't
            > have
            > > > any
            > > > > > data on the Celestron. The chromatic aberration you're
            > seeing is
            > > > > > likely related to this. I saw it in my own web cam. The
            > more
            > > > > > expensive Hutech/IDAS LPS blocks UV and NIR but may not
            > provide
            > > > good
            > > > > > overall color balance for your camera. I think the best
            > solution
            > > > is
            > > > > > to buy the new Baadar UV/NIR cutoff filter for $42. It
            > solves
            > > > this
            > > > > > problem. I bought mine from Alpine Astronomical, but I think
            > > > > > Adirondack now sells them, too.
            > > > > >
            > > > > > Don Goldman
            > > > > > www.astrodon.com
            > > > > >
            > > > > >
            > > > > > --- In ccd-newastro@yahoogroups.com, "ianderca"
            > <ianderca@y...>
            > > > wrote:
            > > > > > > I have just bought a celestron LPR filter, and I notice a
            > > > > > remarkable
            > > > > > > cromatic aberration from my photo with webcam but in visual
            > > > too:
            > > > > > the
            > > > > > > filter produce a red and blu abberration on the opposite
            > side
            > > > of a
            > > > > > > star for example, similar but more accentuated than
            > cromatic
            > > > > > > aberration from stars at low level hight. This is normal?
            > If
            > > > yes ,
            > > > > > > do you mean that you can use this filter only for visual
            > > > > > observation
            > > > > > > of faint object?
            > > > > > >
            > > > > > > please, if someone have any experience about using it I
            > would
            > > > > > > appreciate any information. I wonder if my filter is bad.
            > > > > > >
            > > > > > > best regards
            > > > > > > Alex
          • Bob Holzer
            Don: By any chance have you measured Schuler s Not IR/UV filter? I ve been using it to cut blue bloat on my Tak FS60C with great results, but just wonder how
            Message 5 of 18 , Apr 1, 2004
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              Don:

              By any chance have you measured Schuler's Not IR/UV filter? I've been
              using it to cut blue bloat on my Tak FS60C with great results, but just
              wonder how the numbers actually compare to the Baader.

              Thanks,

              Bob


              -----Original Message-----
              From: Don Goldman [mailto:donclearview@...]
              Sent: Thursday, April 01, 2004 3:11 PM
              To: ccd-newastro@yahoogroups.com
              Subject: [ccd-newastro] Re: question about strange results from LPR
              filter

              Peter, just spectrally measured the Baader filter here at work. The
              small peaks that you see posted at Adirondack below 400 nm are
              there. They amount to only about 4% of a typical blue filter
              transmission, and about 1.5% of the Red+Green+Blue. Since the CCD
              QE drops off so strongly below about 420 nm, these peaks will not
              have much of an effect. I think this is an excellent low-cost filter
              for the web-cams.

              Don Goldman
              www.astrodon.com


              --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...> wrote:
              > The curve that I was referring to was the one on the Adirondack web
              > site. There, below the sharp cut-off at 400nm, is another peak
              > extending down to nearly 300nm. Did the curve that came with your
              > filter extend the data down to 300nm? Certainly moving the cut-off
              to
              > 430nm eats into the blue flux, but unfortunately that seems to be
              > where any APOs that I've seen data on start to become diffraction
              > limited (hence the blue halos otherwise).
              >
              > Peter
              >
              > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
              <donclearview@y...>
              > wrote:
              > > Peter, the scan that came with the Baadar showed very sharp
              cutoffs
              > > at 400 and 700 nm with the UV and NIR blocked.
              > >
              > > I find it hard to accept your premise about a filter that blocks
              up
              > > to 430 nm. That does not leave much in the blue spectral region,
              > > although it will certainly remove blue halos in refractors, as
              does
              > > the minus violet filter from Lumicon.
              > >
              > > Don Goldman
              > > www.astrodon.com
              > >
              > >
              > >
              > > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...>
              wrote:
              > > > The Baader UV/NIR filter does block NIR, and may be the best
              filter
              > > > available for the purpose. But I remain confused how it can be
              > > called
              > > > a UV blocker when it has appreciable transmission down to nearly
              > > > 300nm. At that point atmospheric ozone is the more important
              > > blocker.
              > > >
              > > > I'm still waiting for a properly designed UV/NIR blocker
              suitable
              > > for
              > > > APO refractors, tranmission range of 450-850nm where they are
              mostly
              > > > still diffraction limited. Everything presently cuts off at
              700nm
              > > > (too early, wasting light) and transmits down to below 400nm
              (much
              > > too
              > > > far).
              > > >
              > > > Peter
              > > >
              > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
              > > <donclearview@y...>
              > > > wrote:
              > > > > Alex,
              > > > >
              > > > > The Meade, and I suspect, Celestron LPS filter let near-
              infrared
              > > > > light pass to the web cam. The Meade LPS blocks UV. Don't
              have
              > > any
              > > > > data on the Celestron. The chromatic aberration you're
              seeing is
              > > > > likely related to this. I saw it in my own web cam. The
              more
              > > > > expensive Hutech/IDAS LPS blocks UV and NIR but may not
              provide
              > > good
              > > > > overall color balance for your camera. I think the best
              solution
              > > is
              > > > > to buy the new Baadar UV/NIR cutoff filter for $42. It
              solves
              > > this
              > > > > problem. I bought mine from Alpine Astronomical, but I think
              > > > > Adirondack now sells them, too.
              > > > >
              > > > > Don Goldman
              > > > > www.astrodon.com
              > > > >
              > > > >
              > > > > --- In ccd-newastro@yahoogroups.com, "ianderca"
              <ianderca@y...>
              > > wrote:
              > > > > > I have just bought a celestron LPR filter, and I notice a
              > > > > remarkable
              > > > > > cromatic aberration from my photo with webcam but in visual
              > > too:
              > > > > the
              > > > > > filter produce a red and blu abberration on the opposite
              side
              > > of a
              > > > > > star for example, similar but more accentuated than
              cromatic
              > > > > > aberration from stars at low level hight. This is normal?
              If
              > > yes ,
              > > > > > do you mean that you can use this filter only for visual
              > > > > observation
              > > > > > of faint object?
              > > > > >
              > > > > > please, if someone have any experience about using it I
              would
              > > > > > appreciate any information. I wonder if my filter is bad.
              > > > > >
              > > > > > best regards
              > > > > > Alex





              Yahoo! Groups Links
            • Don Goldman
              Hi, Bob, not familiar with this at all ... been ... just ... I didn t know about the Schuler Not V (=violet) and IR filter , but did a little research. I see
              Message 6 of 18 , Apr 1, 2004
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                Hi, Bob, not familiar with this at all



                --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                wrote:
                > Don:
                >
                > By any chance have you measured Schuler's Not IR/UV filter? I've
                been
                > using it to cut blue bloat on my Tak FS60C with great results, but
                just
                > wonder how the numbers actually compare to the Baader.
                >
                > Thanks,
                >
                > Bob

                I didn't know about the Schuler "Not V (=violet) and IR filter", but
                did a little research. I see Anacortes sells it. No curves
                published, but.........I have my ways. It gradually cuts on where it
                transmits about 50% at 430 nm and then slowly tails down in the NIR
                similar to the Schuler red and luminance filters that I have plotted
                on my web site. This eliminates the blue halos and fringing in the
                less expensive refractors and would be perfect for the web cams,
                likely better than the Baader filter. Peter was right. 400 nm is too
                early to cut out fringing in some of the lower cost refractors.
                That's why Lumicon came out with the -violet filter some time ago.
                For CCD imaging, the blue filter will take a hard hit and you will
                likely have to weight it ~3x compared to green. I think I have been
                unknowingly biased, since my TAK FSQ is so incredibly corrected that
                I don't see the problems that people see in less expensive
                refractors. Hope this helps and thanks for getting me to dig around
                and find out more about this Schuler filter.

                Don Goldman
                www.astrodon.com


                >
                >
                > -----Original Message-----
                > From: Don Goldman [mailto:donclearview@y...]
                > Sent: Thursday, April 01, 2004 3:11 PM
                > To: ccd-newastro@yahoogroups.com
                > Subject: [ccd-newastro] Re: question about strange results from LPR
                > filter
                >
                > Peter, just spectrally measured the Baader filter here at work.
                The
                > small peaks that you see posted at Adirondack below 400 nm are
                > there. They amount to only about 4% of a typical blue filter
                > transmission, and about 1.5% of the Red+Green+Blue. Since the CCD
                > QE drops off so strongly below about 420 nm, these peaks will not
                > have much of an effect. I think this is an excellent low-cost
                filter
                > for the web-cams.
                >
                > Don Goldman
                > www.astrodon.com
                >
                >
                > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...>
                wrote:
                > > The curve that I was referring to was the one on the Adirondack
                web
                > > site. There, below the sharp cut-off at 400nm, is another peak
                > > extending down to nearly 300nm. Did the curve that came with your
                > > filter extend the data down to 300nm? Certainly moving the cut-
                off
                > to
                > > 430nm eats into the blue flux, but unfortunately that seems to be
                > > where any APOs that I've seen data on start to become diffraction
                > > limited (hence the blue halos otherwise).
                > >
                > > Peter
                > >
                > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                > <donclearview@y...>
                > > wrote:
                > > > Peter, the scan that came with the Baadar showed very sharp
                > cutoffs
                > > > at 400 and 700 nm with the UV and NIR blocked.
                > > >
                > > > I find it hard to accept your premise about a filter that
                blocks
                > up
                > > > to 430 nm. That does not leave much in the blue spectral
                region,
                > > > although it will certainly remove blue halos in refractors, as
                > does
                > > > the minus violet filter from Lumicon.
                > > >
                > > > Don Goldman
                > > > www.astrodon.com
                > > >
                > > >
                > > >
                > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...>
                > wrote:
                > > > > The Baader UV/NIR filter does block NIR, and may be the best
                > filter
                > > > > available for the purpose. But I remain confused how it can
                be
                > > > called
                > > > > a UV blocker when it has appreciable transmission down to
                nearly
                > > > > 300nm. At that point atmospheric ozone is the more important
                > > > blocker.
                > > > >
                > > > > I'm still waiting for a properly designed UV/NIR blocker
                > suitable
                > > > for
                > > > > APO refractors, tranmission range of 450-850nm where they are
                > mostly
                > > > > still diffraction limited. Everything presently cuts off at
                > 700nm
                > > > > (too early, wasting light) and transmits down to below 400nm
                > (much
                > > > too
                > > > > far).
                > > > >
                > > > > Peter
                > > > >
                > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                > > > <donclearview@y...>
                > > > > wrote:
                > > > > > Alex,
                > > > > >
                > > > > > The Meade, and I suspect, Celestron LPS filter let near-
                > infrared
                > > > > > light pass to the web cam. The Meade LPS blocks UV. Don't
                > have
                > > > any
                > > > > > data on the Celestron. The chromatic aberration you're
                > seeing is
                > > > > > likely related to this. I saw it in my own web cam. The
                > more
                > > > > > expensive Hutech/IDAS LPS blocks UV and NIR but may not
                > provide
                > > > good
                > > > > > overall color balance for your camera. I think the best
                > solution
                > > > is
                > > > > > to buy the new Baadar UV/NIR cutoff filter for $42. It
                > solves
                > > > this
                > > > > > problem. I bought mine from Alpine Astronomical, but I
                think
                > > > > > Adirondack now sells them, too.
                > > > > >
                > > > > > Don Goldman
                > > > > > www.astrodon.com
                > > > > >
                > > > > >
                > > > > > --- In ccd-newastro@yahoogroups.com, "ianderca"
                > <ianderca@y...>
                > > > wrote:
                > > > > > > I have just bought a celestron LPR filter, and I notice a
                > > > > > remarkable
                > > > > > > cromatic aberration from my photo with webcam but in
                visual
                > > > too:
                > > > > > the
                > > > > > > filter produce a red and blu abberration on the opposite
                > side
                > > > of a
                > > > > > > star for example, similar but more accentuated than
                > cromatic
                > > > > > > aberration from stars at low level hight. This is normal?
                > If
                > > > yes ,
                > > > > > > do you mean that you can use this filter only for visual
                > > > > > observation
                > > > > > > of faint object?
                > > > > > >
                > > > > > > please, if someone have any experience about using it I
                > would
                > > > > > > appreciate any information. I wonder if my filter is bad.
                > > > > > >
                > > > > > > best regards
                > > > > > > Alex
                >
                >
                >
                >
                >
                > Yahoo! Groups Links
              • Don Goldman
                ... For some reason this didn t post. I m resending it now. If it appears twice, sorry about that! I didn t know about the Schuler Not V (=violet) and IR
                Message 7 of 18 , Apr 1, 2004
                • 0 Attachment
                  > Bob

                  For some reason this didn't post. I'm resending it now. If it appears
                  twice, sorry about that!

                  I didn't know about the Schuler "Not V (=violet) and IR filter", but
                  did a little research. I see Anacortes sells it. No curves
                  published, but.........I have my ways. It gradually cuts on where it
                  transmits about 50% at 430 nm and then slowly tails down in the NIR
                  similar to the Schuler red and luminance filters that I have plotted
                  on my web site. This eliminates the blue halos and fringing in the
                  less expensive refractors and would be perfect for the web cams,
                  likely better than the Baader filter. Peter was right. 400 nm is too
                  early to cut out fringing in some of the lower cost refractors.
                  That's why Lumicon came out with the -violet filter some time ago.
                  For CCD imaging, the blue filter will take a hard hit and you will
                  likely have to weight it ~3x compared to green. I think I have been
                  unknowingly biased, since my TAK FSQ is so incredibly corrected that
                  I don't see the problems that people see in less expensive
                  refractors. Hope this helps and thanks for getting me to dig around
                  and find out more about this Schuler filter.

                  Don Goldman
                  www.astrodon.com




                  --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                  wrote:
                  > Don:
                  >
                  > By any chance have you measured Schuler's Not IR/UV filter? I've
                  been
                  > using it to cut blue bloat on my Tak FS60C with great results, but
                  just
                  > wonder how the numbers actually compare to the Baader.
                  >
                  > Thanks,
                  >
                  > Bob
                  >
                  >
                  > -----Original Message-----
                  > From: Don Goldman [mailto:donclearview@y...]
                  > Sent: Thursday, April 01, 2004 3:11 PM
                  > To: ccd-newastro@yahoogroups.com
                  > Subject: [ccd-newastro] Re: question about strange results from LPR
                  > filter
                  >
                  > Peter, just spectrally measured the Baader filter here at work.
                  The
                  > small peaks that you see posted at Adirondack below 400 nm are
                  > there. They amount to only about 4% of a typical blue filter
                  > transmission, and about 1.5% of the Red+Green+Blue. Since the CCD
                  > QE drops off so strongly below about 420 nm, these peaks will not
                  > have much of an effect. I think this is an excellent low-cost
                  filter
                  > for the web-cams.
                  >
                  > Don Goldman
                  > www.astrodon.com
                  >
                  >
                  > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...>
                  wrote:
                  > > The curve that I was referring to was the one on the Adirondack
                  web
                  > > site. There, below the sharp cut-off at 400nm, is another peak
                  > > extending down to nearly 300nm. Did the curve that came with your
                  > > filter extend the data down to 300nm? Certainly moving the cut-
                  off
                  > to
                  > > 430nm eats into the blue flux, but unfortunately that seems to be
                  > > where any APOs that I've seen data on start to become diffraction
                  > > limited (hence the blue halos otherwise).
                  > >
                  > > Peter
                  > >
                  > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                  > <donclearview@y...>
                  > > wrote:
                  > > > Peter, the scan that came with the Baadar showed very sharp
                  > cutoffs
                  > > > at 400 and 700 nm with the UV and NIR blocked.
                  > > >
                  > > > I find it hard to accept your premise about a filter that
                  blocks
                  > up
                  > > > to 430 nm. That does not leave much in the blue spectral
                  region,
                  > > > although it will certainly remove blue halos in refractors, as
                  > does
                  > > > the minus violet filter from Lumicon.
                  > > >
                  > > > Don Goldman
                  > > > www.astrodon.com
                  > > >
                  > > >
                  > > >
                  > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...>
                  > wrote:
                  > > > > The Baader UV/NIR filter does block NIR, and may be the best
                  > filter
                  > > > > available for the purpose. But I remain confused how it can
                  be
                  > > > called
                  > > > > a UV blocker when it has appreciable transmission down to
                  nearly
                  > > > > 300nm. At that point atmospheric ozone is the more important
                  > > > blocker.
                  > > > >
                  > > > > I'm still waiting for a properly designed UV/NIR blocker
                  > suitable
                  > > > for
                  > > > > APO refractors, tranmission range of 450-850nm where they are
                  > mostly
                  > > > > still diffraction limited. Everything presently cuts off at
                  > 700nm
                  > > > > (too early, wasting light) and transmits down to below 400nm
                  > (much
                  > > > too
                  > > > > far).
                  > > > >
                  > > > > Peter
                  > > > >
                  > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                  > > > <donclearview@y...>
                  > > > > wrote:
                  > > > > > Alex,
                  > > > > >
                  > > > > > The Meade, and I suspect, Celestron LPS filter let near-
                  > infrared
                  > > > > > light pass to the web cam. The Meade LPS blocks UV. Don't
                  > have
                  > > > any
                  > > > > > data on the Celestron. The chromatic aberration you're
                  > seeing is
                  > > > > > likely related to this. I saw it in my own web cam. The
                  > more
                  > > > > > expensive Hutech/IDAS LPS blocks UV and NIR but may not
                  > provide
                  > > > good
                  > > > > > overall color balance for your camera. I think the best
                  > solution
                  > > > is
                  > > > > > to buy the new Baadar UV/NIR cutoff filter for $42. It
                  > solves
                  > > > this
                  > > > > > problem. I bought mine from Alpine Astronomical, but I
                  think
                  > > > > > Adirondack now sells them, too.
                  > > > > >
                  > > > > > Don Goldman
                  > > > > > www.astrodon.com
                  > > > > >
                  > > > > >
                  > > > > > --- In ccd-newastro@yahoogroups.com, "ianderca"
                  > <ianderca@y...>
                  > > > wrote:
                  > > > > > > I have just bought a celestron LPR filter, and I notice a
                  > > > > > remarkable
                  > > > > > > cromatic aberration from my photo with webcam but in
                  visual
                  > > > too:
                  > > > > > the
                  > > > > > > filter produce a red and blu abberration on the opposite
                  > side
                  > > > of a
                  > > > > > > star for example, similar but more accentuated than
                  > cromatic
                  > > > > > > aberration from stars at low level hight. This is normal?
                  > If
                  > > > yes ,
                  > > > > > > do you mean that you can use this filter only for visual
                  > > > > > observation
                  > > > > > > of faint object?
                  > > > > > >
                  > > > > > > please, if someone have any experience about using it I
                  > would
                  > > > > > > appreciate any information. I wonder if my filter is bad.
                  > > > > > >
                  > > > > > > best regards
                  > > > > > > Alex
                  >
                  >
                  >
                  >
                  >
                  > Yahoo! Groups Links
                • Bob Holzer
                  Hi Don: You might find this interesting. Here is a before and after of M31 from my Tak FS60C, with and without the Schuler filter. Please pardon the magenta
                  Message 8 of 18 , Apr 1, 2004
                  • 0 Attachment
                    Hi Don:

                    You might find this interesting.

                    Here is a before and after of M31 from my Tak FS60C, with and without
                    the Schuler filter. Please pardon the magenta cast to the images as they
                    were done before I calibrated my monitor with a Spyder. I certainly need
                    to go back and fix them <g>.

                    No filter: http://www.bobholzer.com/m31fs60cfinal.jpg
                    Filter: http://www.bobholzer.com/m31lrgbfs60c.jpg

                    Big difference, eh? My Tak FSQ-106 certainly doesn't need the filter
                    either.

                    BTW, if you would like to borrow this filter to test, let me know. I
                    have 2 of them. Or if you would like one, would you take a partial trade
                    for one of your Ha filters <g>? Besides, it's galaxy season so the wide
                    field FS60C is not seeing any light.

                    Bob





                    -----Original Message-----
                    From: Don Goldman [mailto:donclearview@...]
                    Sent: Thursday, April 01, 2004 7:13 PM
                    To: ccd-newastro@yahoogroups.com
                    Subject: [ccd-newastro] Re: question about strange results from LPR
                    filter

                    > Bob

                    For some reason this didn't post. I'm resending it now. If it appears
                    twice, sorry about that!

                    I didn't know about the Schuler "Not V (=violet) and IR filter", but
                    did a little research. I see Anacortes sells it. No curves
                    published, but.........I have my ways. It gradually cuts on where it
                    transmits about 50% at 430 nm and then slowly tails down in the NIR
                    similar to the Schuler red and luminance filters that I have plotted
                    on my web site. This eliminates the blue halos and fringing in the
                    less expensive refractors and would be perfect for the web cams,
                    likely better than the Baader filter. Peter was right. 400 nm is too
                    early to cut out fringing in some of the lower cost refractors.
                    That's why Lumicon came out with the -violet filter some time ago.
                    For CCD imaging, the blue filter will take a hard hit and you will
                    likely have to weight it ~3x compared to green. I think I have been
                    unknowingly biased, since my TAK FSQ is so incredibly corrected that
                    I don't see the problems that people see in less expensive
                    refractors. Hope this helps and thanks for getting me to dig around
                    and find out more about this Schuler filter.

                    Don Goldman
                    www.astrodon.com




                    --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                    wrote:
                    > Don:
                    >
                    > By any chance have you measured Schuler's Not IR/UV filter? I've
                    been
                    > using it to cut blue bloat on my Tak FS60C with great results, but
                    just
                    > wonder how the numbers actually compare to the Baader.
                    >
                    > Thanks,
                    >
                    > Bob
                    >
                    >
                    > -----Original Message-----
                    > From: Don Goldman [mailto:donclearview@y...]
                    > Sent: Thursday, April 01, 2004 3:11 PM
                    > To: ccd-newastro@yahoogroups.com
                    > Subject: [ccd-newastro] Re: question about strange results from LPR
                    > filter
                    >
                    > Peter, just spectrally measured the Baader filter here at work.
                    The
                    > small peaks that you see posted at Adirondack below 400 nm are
                    > there. They amount to only about 4% of a typical blue filter
                    > transmission, and about 1.5% of the Red+Green+Blue. Since the CCD
                    > QE drops off so strongly below about 420 nm, these peaks will not
                    > have much of an effect. I think this is an excellent low-cost
                    filter
                    > for the web-cams.
                    >
                    > Don Goldman
                    > www.astrodon.com
                    >
                    >
                    > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...>
                    wrote:
                    > > The curve that I was referring to was the one on the Adirondack
                    web
                    > > site. There, below the sharp cut-off at 400nm, is another peak
                    > > extending down to nearly 300nm. Did the curve that came with your
                    > > filter extend the data down to 300nm? Certainly moving the cut-
                    off
                    > to
                    > > 430nm eats into the blue flux, but unfortunately that seems to be
                    > > where any APOs that I've seen data on start to become diffraction
                    > > limited (hence the blue halos otherwise).
                    > >
                    > > Peter
                    > >
                    > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                    > <donclearview@y...>
                    > > wrote:
                    > > > Peter, the scan that came with the Baadar showed very sharp
                    > cutoffs
                    > > > at 400 and 700 nm with the UV and NIR blocked.
                    > > >
                    > > > I find it hard to accept your premise about a filter that
                    blocks
                    > up
                    > > > to 430 nm. That does not leave much in the blue spectral
                    region,
                    > > > although it will certainly remove blue halos in refractors, as
                    > does
                    > > > the minus violet filter from Lumicon.
                    > > >
                    > > > Don Goldman
                    > > > www.astrodon.com
                    > > >
                    > > >
                    > > >
                    > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...>
                    > wrote:
                    > > > > The Baader UV/NIR filter does block NIR, and may be the best
                    > filter
                    > > > > available for the purpose. But I remain confused how it can
                    be
                    > > > called
                    > > > > a UV blocker when it has appreciable transmission down to
                    nearly
                    > > > > 300nm. At that point atmospheric ozone is the more important
                    > > > blocker.
                    > > > >
                    > > > > I'm still waiting for a properly designed UV/NIR blocker
                    > suitable
                    > > > for
                    > > > > APO refractors, tranmission range of 450-850nm where they are
                    > mostly
                    > > > > still diffraction limited. Everything presently cuts off at
                    > 700nm
                    > > > > (too early, wasting light) and transmits down to below 400nm
                    > (much
                    > > > too
                    > > > > far).
                    > > > >
                    > > > > Peter
                    > > > >
                    > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                    > > > <donclearview@y...>
                    > > > > wrote:
                    > > > > > Alex,
                    > > > > >
                    > > > > > The Meade, and I suspect, Celestron LPS filter let near-
                    > infrared
                    > > > > > light pass to the web cam. The Meade LPS blocks UV. Don't
                    > have
                    > > > any
                    > > > > > data on the Celestron. The chromatic aberration you're
                    > seeing is
                    > > > > > likely related to this. I saw it in my own web cam. The
                    > more
                    > > > > > expensive Hutech/IDAS LPS blocks UV and NIR but may not
                    > provide
                    > > > good
                    > > > > > overall color balance for your camera. I think the best
                    > solution
                    > > > is
                    > > > > > to buy the new Baadar UV/NIR cutoff filter for $42. It
                    > solves
                    > > > this
                    > > > > > problem. I bought mine from Alpine Astronomical, but I
                    think
                    > > > > > Adirondack now sells them, too.
                    > > > > >
                    > > > > > Don Goldman
                    > > > > > www.astrodon.com
                    > > > > >
                    > > > > >
                    > > > > > --- In ccd-newastro@yahoogroups.com, "ianderca"
                    > <ianderca@y...>
                    > > > wrote:
                    > > > > > > I have just bought a celestron LPR filter, and I notice a
                    > > > > > remarkable
                    > > > > > > cromatic aberration from my photo with webcam but in
                    visual
                    > > > too:
                    > > > > > the
                    > > > > > > filter produce a red and blu abberration on the opposite
                    > side
                    > > > of a
                    > > > > > > star for example, similar but more accentuated than
                    > cromatic
                    > > > > > > aberration from stars at low level hight. This is normal?
                    > If
                    > > > yes ,
                    > > > > > > do you mean that you can use this filter only for visual
                    > > > > > observation
                    > > > > > > of faint object?
                    > > > > > >
                    > > > > > > please, if someone have any experience about using it I
                    > would
                    > > > > > > appreciate any information. I wonder if my filter is bad.
                    > > > > > >
                    > > > > > > best regards
                    > > > > > > Alex
                    >
                    >
                    >
                    >
                    >
                    > Yahoo! Groups Links





                    Yahoo! Groups Links
                  • Jon Talbot
                    Don, I use the Schuler filter with my Stellarvue Nighthawk Achromat and find it works best in reducing the blue halo s I did a little test comparing the
                    Message 9 of 18 , Apr 2, 2004
                    • 0 Attachment
                      Don, I use the Schuler filter with my Stellarvue Nighthawk Achromat
                      and find it works best in reducing the blue halo's I did a little
                      test comparing the Baader Fringe Killer with the Schuler and the
                      Schuler won. There wasnt alot of science in this test just visual
                      impression. Here is the link.
                      http://www.myweb.cableone.net/hurricane4/Filter Test.html

                      I find I need to weight the blue frame about 2x compared to green
                      using the SXV-H9. Here are two images I've taken with the Schuler
                      filter. Not too bad for a Achromat!

                      http://www.myweb.cableone.net/hurricane4/M67_031804.html
                      http://www.myweb.cableone.net/hurricane4/M78_012204.html

                      Jon Talbot


                      --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                      wrote:
                      > Hi Don:
                      >
                      > You might find this interesting.
                      >
                      > Here is a before and after of M31 from my Tak FS60C, with and
                      without
                      > the Schuler filter. Please pardon the magenta cast to the images as
                      they
                      > were done before I calibrated my monitor with a Spyder. I certainly
                      need
                      > to go back and fix them <g>.
                      >
                      > No filter: http://www.bobholzer.com/m31fs60cfinal.jpg
                      > Filter: http://www.bobholzer.com/m31lrgbfs60c.jpg
                      >
                      > Big difference, eh? My Tak FSQ-106 certainly doesn't need the filter
                      > either.
                      >
                      > BTW, if you would like to borrow this filter to test, let me know. I
                      > have 2 of them. Or if you would like one, would you take a partial
                      trade
                      > for one of your Ha filters <g>? Besides, it's galaxy season so the
                      wide
                      > field FS60C is not seeing any light.
                      >
                      > Bob
                      >
                      >
                      >
                      >
                      >
                      > -----Original Message-----
                      > From: Don Goldman [mailto:donclearview@y...]
                      > Sent: Thursday, April 01, 2004 7:13 PM
                      > To: ccd-newastro@yahoogroups.com
                      > Subject: [ccd-newastro] Re: question about strange results from LPR
                      > filter
                      >
                      > > Bob
                      >
                      > For some reason this didn't post. I'm resending it now. If it
                      appears
                      > twice, sorry about that!
                      >
                      > I didn't know about the Schuler "Not V (=violet) and IR filter",
                      but
                      > did a little research. I see Anacortes sells it. No curves
                      > published, but.........I have my ways. It gradually cuts on where
                      it
                      > transmits about 50% at 430 nm and then slowly tails down in the NIR
                      > similar to the Schuler red and luminance filters that I have
                      plotted
                      > on my web site. This eliminates the blue halos and fringing in the
                      > less expensive refractors and would be perfect for the web cams,
                      > likely better than the Baader filter. Peter was right. 400 nm is
                      too
                      > early to cut out fringing in some of the lower cost refractors.
                      > That's why Lumicon came out with the -violet filter some time
                      ago.
                      > For CCD imaging, the blue filter will take a hard hit and you will
                      > likely have to weight it ~3x compared to green. I think I have
                      been
                      > unknowingly biased, since my TAK FSQ is so incredibly corrected
                      that
                      > I don't see the problems that people see in less expensive
                      > refractors. Hope this helps and thanks for getting me to dig
                      around
                      > and find out more about this Schuler filter.
                      >
                      > Don Goldman
                      > www.astrodon.com
                      >
                      >
                      >
                      >
                      > --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                      > wrote:
                      > > Don:
                      > >
                      > > By any chance have you measured Schuler's Not IR/UV filter? I've
                      > been
                      > > using it to cut blue bloat on my Tak FS60C with great results,
                      but
                      > just
                      > > wonder how the numbers actually compare to the Baader.
                      > >
                      > > Thanks,
                      > >
                      > > Bob
                      > >
                      > >
                      > > -----Original Message-----
                      > > From: Don Goldman [mailto:donclearview@y...]
                      > > Sent: Thursday, April 01, 2004 3:11 PM
                      > > To: ccd-newastro@yahoogroups.com
                      > > Subject: [ccd-newastro] Re: question about strange results from
                      LPR
                      > > filter
                      > >
                      > > Peter, just spectrally measured the Baader filter here at work.
                      > The
                      > > small peaks that you see posted at Adirondack below 400 nm are
                      > > there. They amount to only about 4% of a typical blue filter
                      > > transmission, and about 1.5% of the Red+Green+Blue. Since the
                      CCD
                      > > QE drops off so strongly below about 420 nm, these peaks will not
                      > > have much of an effect. I think this is an excellent low-cost
                      > filter
                      > > for the web-cams.
                      > >
                      > > Don Goldman
                      > > www.astrodon.com
                      > >
                      > >
                      > > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...>
                      > wrote:
                      > > > The curve that I was referring to was the one on the Adirondack
                      > web
                      > > > site. There, below the sharp cut-off at 400nm, is another peak
                      > > > extending down to nearly 300nm. Did the curve that came with
                      your
                      > > > filter extend the data down to 300nm? Certainly moving the cut-
                      > off
                      > > to
                      > > > 430nm eats into the blue flux, but unfortunately that seems to
                      be
                      > > > where any APOs that I've seen data on start to become
                      diffraction
                      > > > limited (hence the blue halos otherwise).
                      > > >
                      > > > Peter
                      > > >
                      > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                      > > <donclearview@y...>
                      > > > wrote:
                      > > > > Peter, the scan that came with the Baadar showed very sharp
                      > > cutoffs
                      > > > > at 400 and 700 nm with the UV and NIR blocked.
                      > > > >
                      > > > > I find it hard to accept your premise about a filter that
                      > blocks
                      > > up
                      > > > > to 430 nm. That does not leave much in the blue spectral
                      > region,
                      > > > > although it will certainly remove blue halos in refractors,
                      as
                      > > does
                      > > > > the minus violet filter from Lumicon.
                      > > > >
                      > > > > Don Goldman
                      > > > > www.astrodon.com
                      > > > >
                      > > > >
                      > > > >
                      > > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe"
                      <erdmanp@e...>
                      > > wrote:
                      > > > > > The Baader UV/NIR filter does block NIR, and may be the
                      best
                      > > filter
                      > > > > > available for the purpose. But I remain confused how it
                      can
                      > be
                      > > > > called
                      > > > > > a UV blocker when it has appreciable transmission down to
                      > nearly
                      > > > > > 300nm. At that point atmospheric ozone is the more
                      important
                      > > > > blocker.
                      > > > > >
                      > > > > > I'm still waiting for a properly designed UV/NIR blocker
                      > > suitable
                      > > > > for
                      > > > > > APO refractors, tranmission range of 450-850nm where they
                      are
                      > > mostly
                      > > > > > still diffraction limited. Everything presently cuts off
                      at
                      > > 700nm
                      > > > > > (too early, wasting light) and transmits down to below
                      400nm
                      > > (much
                      > > > > too
                      > > > > > far).
                      > > > > >
                      > > > > > Peter
                      > > > > >
                      > > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                      > > > > <donclearview@y...>
                      > > > > > wrote:
                      > > > > > > Alex,
                      > > > > > >
                      > > > > > > The Meade, and I suspect, Celestron LPS filter let near-
                      > > infrared
                      > > > > > > light pass to the web cam. The Meade LPS blocks UV.
                      Don't
                      > > have
                      > > > > any
                      > > > > > > data on the Celestron. The chromatic aberration you're
                      > > seeing is
                      > > > > > > likely related to this. I saw it in my own web cam. The
                      > > more
                      > > > > > > expensive Hutech/IDAS LPS blocks UV and NIR but may not
                      > > provide
                      > > > > good
                      > > > > > > overall color balance for your camera. I think the best
                      > > solution
                      > > > > is
                      > > > > > > to buy the new Baadar UV/NIR cutoff filter for $42. It
                      > > solves
                      > > > > this
                      > > > > > > problem. I bought mine from Alpine Astronomical, but I
                      > think
                      > > > > > > Adirondack now sells them, too.
                      > > > > > >
                      > > > > > > Don Goldman
                      > > > > > > www.astrodon.com
                      > > > > > >
                      > > > > > >
                      > > > > > > --- In ccd-newastro@yahoogroups.com, "ianderca"
                      > > <ianderca@y...>
                      > > > > wrote:
                      > > > > > > > I have just bought a celestron LPR filter, and I notice
                      a
                      > > > > > > remarkable
                      > > > > > > > cromatic aberration from my photo with webcam but in
                      > visual
                      > > > > too:
                      > > > > > > the
                      > > > > > > > filter produce a red and blu abberration on the
                      opposite
                      > > side
                      > > > > of a
                      > > > > > > > star for example, similar but more accentuated than
                      > > cromatic
                      > > > > > > > aberration from stars at low level hight. This is
                      normal?
                      > > If
                      > > > > yes ,
                      > > > > > > > do you mean that you can use this filter only for
                      visual
                      > > > > > > observation
                      > > > > > > > of faint object?
                      > > > > > > >
                      > > > > > > > please, if someone have any experience about using it I
                      > > would
                      > > > > > > > appreciate any information. I wonder if my filter is
                      bad.
                      > > > > > > >
                      > > > > > > > best regards
                      > > > > > > > Alex
                      > >
                      > >
                      > >
                      > >
                      > >
                      > > Yahoo! Groups Links
                      >
                      >
                      >
                      >
                      >
                      > Yahoo! Groups Links
                    • Don Goldman
                      John, Chet Schuler designed this filter for this very reason. For less corrected scopes, and achromats will certainly be in this group, the Schuler filter
                      Message 10 of 18 , Apr 2, 2004
                      • 0 Attachment
                        John, Chet Schuler designed this filter for this very reason. For
                        less corrected scopes, and achromats will certainly be in this group,
                        the Schuler filter should be much better than the Baader even though
                        you take a big light hit in the blue filter. It is not surprising
                        that you needed a much higher weight. So, this is all consistent.
                        The FSQ and perhaps the NP101 and AP155 may not need such a severe
                        approach.

                        Don Goldman
                        www.astrodon.com


                        --- In ccd-newastro@yahoogroups.com, "Jon Talbot" <hurricane4@c...>
                        wrote:
                        > Don, I use the Schuler filter with my Stellarvue Nighthawk Achromat
                        > and find it works best in reducing the blue halo's I did a little
                        > test comparing the Baader Fringe Killer with the Schuler and the
                        > Schuler won. There wasnt alot of science in this test just visual
                        > impression. Here is the link.
                        > http://www.myweb.cableone.net/hurricane4/Filter Test.html
                        >
                        > I find I need to weight the blue frame about 2x compared to green
                        > using the SXV-H9. Here are two images I've taken with the Schuler
                        > filter. Not too bad for a Achromat!
                        >
                        > http://www.myweb.cableone.net/hurricane4/M67_031804.html
                        > http://www.myweb.cableone.net/hurricane4/M78_012204.html
                        >
                        > Jon Talbot
                        >
                        >
                        > --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                        > wrote:
                        > > Hi Don:
                        > >
                        > > You might find this interesting.
                        > >
                        > > Here is a before and after of M31 from my Tak FS60C, with and
                        > without
                        > > the Schuler filter. Please pardon the magenta cast to the images
                        as
                        > they
                        > > were done before I calibrated my monitor with a Spyder. I
                        certainly
                        > need
                        > > to go back and fix them <g>.
                        > >
                        > > No filter: http://www.bobholzer.com/m31fs60cfinal.jpg
                        > > Filter: http://www.bobholzer.com/m31lrgbfs60c.jpg
                        > >
                        > > Big difference, eh? My Tak FSQ-106 certainly doesn't need the
                        filter
                        > > either.
                        > >
                        > > BTW, if you would like to borrow this filter to test, let me
                        know. I
                        > > have 2 of them. Or if you would like one, would you take a
                        partial
                        > trade
                        > > for one of your Ha filters <g>? Besides, it's galaxy season so
                        the
                        > wide
                        > > field FS60C is not seeing any light.
                        > >
                        > > Bob
                        > >
                        > >
                        > >
                        > >
                        > >
                        > > -----Original Message-----
                        > > From: Don Goldman [mailto:donclearview@y...]
                        > > Sent: Thursday, April 01, 2004 7:13 PM
                        > > To: ccd-newastro@yahoogroups.com
                        > > Subject: [ccd-newastro] Re: question about strange results from
                        LPR
                        > > filter
                        > >
                        > > > Bob
                        > >
                        > > For some reason this didn't post. I'm resending it now. If it
                        > appears
                        > > twice, sorry about that!
                        > >
                        > > I didn't know about the Schuler "Not V (=violet) and IR filter",
                        > but
                        > > did a little research. I see Anacortes sells it. No curves
                        > > published, but.........I have my ways. It gradually cuts on
                        where
                        > it
                        > > transmits about 50% at 430 nm and then slowly tails down in the
                        NIR
                        > > similar to the Schuler red and luminance filters that I have
                        > plotted
                        > > on my web site. This eliminates the blue halos and fringing in
                        the
                        > > less expensive refractors and would be perfect for the web cams,
                        > > likely better than the Baader filter. Peter was right. 400 nm is
                        > too
                        > > early to cut out fringing in some of the lower cost refractors.
                        > > That's why Lumicon came out with the -violet filter some time
                        > ago.
                        > > For CCD imaging, the blue filter will take a hard hit and you
                        will
                        > > likely have to weight it ~3x compared to green. I think I have
                        > been
                        > > unknowingly biased, since my TAK FSQ is so incredibly corrected
                        > that
                        > > I don't see the problems that people see in less expensive
                        > > refractors. Hope this helps and thanks for getting me to dig
                        > around
                        > > and find out more about this Schuler filter.
                        > >
                        > > Don Goldman
                        > > www.astrodon.com
                        > >
                        > >
                        > >
                        > >
                        > > --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                        > > wrote:
                        > > > Don:
                        > > >
                        > > > By any chance have you measured Schuler's Not IR/UV filter?
                        I've
                        > > been
                        > > > using it to cut blue bloat on my Tak FS60C with great results,
                        > but
                        > > just
                        > > > wonder how the numbers actually compare to the Baader.
                        > > >
                        > > > Thanks,
                        > > >
                        > > > Bob
                        > > >
                        > > >
                        > > > -----Original Message-----
                        > > > From: Don Goldman [mailto:donclearview@y...]
                        > > > Sent: Thursday, April 01, 2004 3:11 PM
                        > > > To: ccd-newastro@yahoogroups.com
                        > > > Subject: [ccd-newastro] Re: question about strange results from
                        > LPR
                        > > > filter
                        > > >
                        > > > Peter, just spectrally measured the Baader filter here at
                        work.
                        > > The
                        > > > small peaks that you see posted at Adirondack below 400 nm are
                        > > > there. They amount to only about 4% of a typical blue filter
                        > > > transmission, and about 1.5% of the Red+Green+Blue. Since the
                        > CCD
                        > > > QE drops off so strongly below about 420 nm, these peaks will
                        not
                        > > > have much of an effect. I think this is an excellent low-cost
                        > > filter
                        > > > for the web-cams.
                        > > >
                        > > > Don Goldman
                        > > > www.astrodon.com
                        > > >
                        > > >
                        > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...>
                        > > wrote:
                        > > > > The curve that I was referring to was the one on the
                        Adirondack
                        > > web
                        > > > > site. There, below the sharp cut-off at 400nm, is another
                        peak
                        > > > > extending down to nearly 300nm. Did the curve that came with
                        > your
                        > > > > filter extend the data down to 300nm? Certainly moving the
                        cut-
                        > > off
                        > > > to
                        > > > > 430nm eats into the blue flux, but unfortunately that seems
                        to
                        > be
                        > > > > where any APOs that I've seen data on start to become
                        > diffraction
                        > > > > limited (hence the blue halos otherwise).
                        > > > >
                        > > > > Peter
                        > > > >
                        > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                        > > > <donclearview@y...>
                        > > > > wrote:
                        > > > > > Peter, the scan that came with the Baadar showed very sharp
                        > > > cutoffs
                        > > > > > at 400 and 700 nm with the UV and NIR blocked.
                        > > > > >
                        > > > > > I find it hard to accept your premise about a filter that
                        > > blocks
                        > > > up
                        > > > > > to 430 nm. That does not leave much in the blue spectral
                        > > region,
                        > > > > > although it will certainly remove blue halos in refractors,
                        > as
                        > > > does
                        > > > > > the minus violet filter from Lumicon.
                        > > > > >
                        > > > > > Don Goldman
                        > > > > > www.astrodon.com
                        > > > > >
                        > > > > >
                        > > > > >
                        > > > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe"
                        > <erdmanp@e...>
                        > > > wrote:
                        > > > > > > The Baader UV/NIR filter does block NIR, and may be the
                        > best
                        > > > filter
                        > > > > > > available for the purpose. But I remain confused how it
                        > can
                        > > be
                        > > > > > called
                        > > > > > > a UV blocker when it has appreciable transmission down to
                        > > nearly
                        > > > > > > 300nm. At that point atmospheric ozone is the more
                        > important
                        > > > > > blocker.
                        > > > > > >
                        > > > > > > I'm still waiting for a properly designed UV/NIR blocker
                        > > > suitable
                        > > > > > for
                        > > > > > > APO refractors, tranmission range of 450-850nm where they
                        > are
                        > > > mostly
                        > > > > > > still diffraction limited. Everything presently cuts off
                        > at
                        > > > 700nm
                        > > > > > > (too early, wasting light) and transmits down to below
                        > 400nm
                        > > > (much
                        > > > > > too
                        > > > > > > far).
                        > > > > > >
                        > > > > > > Peter
                        > > > > > >
                        > > > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                        > > > > > <donclearview@y...>
                        > > > > > > wrote:
                        > > > > > > > Alex,
                        > > > > > > >
                        > > > > > > > The Meade, and I suspect, Celestron LPS filter let near-
                        > > > infrared
                        > > > > > > > light pass to the web cam. The Meade LPS blocks UV.
                        > Don't
                        > > > have
                        > > > > > any
                        > > > > > > > data on the Celestron. The chromatic aberration you're
                        > > > seeing is
                        > > > > > > > likely related to this. I saw it in my own web cam.
                        The
                        > > > more
                        > > > > > > > expensive Hutech/IDAS LPS blocks UV and NIR but may not
                        > > > provide
                        > > > > > good
                        > > > > > > > overall color balance for your camera. I think the best
                        > > > solution
                        > > > > > is
                        > > > > > > > to buy the new Baadar UV/NIR cutoff filter for $42. It
                        > > > solves
                        > > > > > this
                        > > > > > > > problem. I bought mine from Alpine Astronomical, but I
                        > > think
                        > > > > > > > Adirondack now sells them, too.
                        > > > > > > >
                        > > > > > > > Don Goldman
                        > > > > > > > www.astrodon.com
                        > > > > > > >
                        > > > > > > >
                        > > > > > > > --- In ccd-newastro@yahoogroups.com, "ianderca"
                        > > > <ianderca@y...>
                        > > > > > wrote:
                        > > > > > > > > I have just bought a celestron LPR filter, and I
                        notice
                        > a
                        > > > > > > > remarkable
                        > > > > > > > > cromatic aberration from my photo with webcam but in
                        > > visual
                        > > > > > too:
                        > > > > > > > the
                        > > > > > > > > filter produce a red and blu abberration on the
                        > opposite
                        > > > side
                        > > > > > of a
                        > > > > > > > > star for example, similar but more accentuated than
                        > > > cromatic
                        > > > > > > > > aberration from stars at low level hight. This is
                        > normal?
                        > > > If
                        > > > > > yes ,
                        > > > > > > > > do you mean that you can use this filter only for
                        > visual
                        > > > > > > > observation
                        > > > > > > > > of faint object?
                        > > > > > > > >
                        > > > > > > > > please, if someone have any experience about using it
                        I
                        > > > would
                        > > > > > > > > appreciate any information. I wonder if my filter is
                        > bad.
                        > > > > > > > >
                        > > > > > > > > best regards
                        > > > > > > > > Alex
                        > > >
                        > > >
                        > > >
                        > > >
                        > > >
                        > > > Yahoo! Groups Links
                        > >
                        > >
                        > >
                        > >
                        > >
                        > > Yahoo! Groups Links
                      • erdmanpe
                        It would be fine if I were corrected, but didn t Wodaski have a web page on reducing blue bloat in an FSQ with a UV reject filter? The only reason I might
                        Message 11 of 18 , Apr 2, 2004
                        • 0 Attachment
                          It would be fine if I were corrected, but didn't Wodaski have a web
                          page on reducing blue bloat in an FSQ with a UV reject filter? The
                          only reason I might remember it is because I was so surprised it might
                          need such a filter.

                          Peter

                          --- In ccd-newastro@yahoogroups.com, "Don Goldman" <donclearview@y...>
                          wrote:
                          > John, Chet Schuler designed this filter for this very reason. For
                          > less corrected scopes, and achromats will certainly be in this group,
                          > the Schuler filter should be much better than the Baader even though
                          > you take a big light hit in the blue filter. It is not surprising
                          > that you needed a much higher weight. So, this is all consistent.
                          > The FSQ and perhaps the NP101 and AP155 may not need such a severe
                          > approach.
                          >
                          > Don Goldman
                          > www.astrodon.com
                          >
                          >
                          > --- In ccd-newastro@yahoogroups.com, "Jon Talbot" <hurricane4@c...>
                          > wrote:
                          > > Don, I use the Schuler filter with my Stellarvue Nighthawk Achromat
                          > > and find it works best in reducing the blue halo's I did a little
                          > > test comparing the Baader Fringe Killer with the Schuler and the
                          > > Schuler won. There wasnt alot of science in this test just visual
                          > > impression. Here is the link.
                          > > http://www.myweb.cableone.net/hurricane4/Filter Test.html
                          > >
                          > > I find I need to weight the blue frame about 2x compared to green
                          > > using the SXV-H9. Here are two images I've taken with the Schuler
                          > > filter. Not too bad for a Achromat!
                          > >
                          > > http://www.myweb.cableone.net/hurricane4/M67_031804.html
                          > > http://www.myweb.cableone.net/hurricane4/M78_012204.html
                          > >
                          > > Jon Talbot
                          > >
                          > >
                          > > --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                          > > wrote:
                          > > > Hi Don:
                          > > >
                          > > > You might find this interesting.
                          > > >
                          > > > Here is a before and after of M31 from my Tak FS60C, with and
                          > > without
                          > > > the Schuler filter. Please pardon the magenta cast to the images
                          > as
                          > > they
                          > > > were done before I calibrated my monitor with a Spyder. I
                          > certainly
                          > > need
                          > > > to go back and fix them <g>.
                          > > >
                          > > > No filter: http://www.bobholzer.com/m31fs60cfinal.jpg
                          > > > Filter: http://www.bobholzer.com/m31lrgbfs60c.jpg
                          > > >
                          > > > Big difference, eh? My Tak FSQ-106 certainly doesn't need the
                          > filter
                          > > > either.
                          > > >
                          > > > BTW, if you would like to borrow this filter to test, let me
                          > know. I
                          > > > have 2 of them. Or if you would like one, would you take a
                          > partial
                          > > trade
                          > > > for one of your Ha filters <g>? Besides, it's galaxy season so
                          > the
                          > > wide
                          > > > field FS60C is not seeing any light.
                          > > >
                          > > > Bob
                          > > >
                          > > >
                          > > >
                          > > >
                          > > >
                          > > > -----Original Message-----
                          > > > From: Don Goldman [mailto:donclearview@y...]
                          > > > Sent: Thursday, April 01, 2004 7:13 PM
                          > > > To: ccd-newastro@yahoogroups.com
                          > > > Subject: [ccd-newastro] Re: question about strange results from
                          > LPR
                          > > > filter
                          > > >
                          > > > > Bob
                          > > >
                          > > > For some reason this didn't post. I'm resending it now. If it
                          > > appears
                          > > > twice, sorry about that!
                          > > >
                          > > > I didn't know about the Schuler "Not V (=violet) and IR filter",
                          > > but
                          > > > did a little research. I see Anacortes sells it. No curves
                          > > > published, but.........I have my ways. It gradually cuts on
                          > where
                          > > it
                          > > > transmits about 50% at 430 nm and then slowly tails down in the
                          > NIR
                          > > > similar to the Schuler red and luminance filters that I have
                          > > plotted
                          > > > on my web site. This eliminates the blue halos and fringing in
                          > the
                          > > > less expensive refractors and would be perfect for the web cams,
                          > > > likely better than the Baader filter. Peter was right. 400 nm is
                          > > too
                          > > > early to cut out fringing in some of the lower cost refractors.
                          > > > That's why Lumicon came out with the -violet filter some time
                          > > ago.
                          > > > For CCD imaging, the blue filter will take a hard hit and you
                          > will
                          > > > likely have to weight it ~3x compared to green. I think I have
                          > > been
                          > > > unknowingly biased, since my TAK FSQ is so incredibly corrected
                          > > that
                          > > > I don't see the problems that people see in less expensive
                          > > > refractors. Hope this helps and thanks for getting me to dig
                          > > around
                          > > > and find out more about this Schuler filter.
                          > > >
                          > > > Don Goldman
                          > > > www.astrodon.com
                          > > >
                          > > >
                          > > >
                          > > >
                          > > > --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                          > > > wrote:
                          > > > > Don:
                          > > > >
                          > > > > By any chance have you measured Schuler's Not IR/UV filter?
                          > I've
                          > > > been
                          > > > > using it to cut blue bloat on my Tak FS60C with great results,
                          > > but
                          > > > just
                          > > > > wonder how the numbers actually compare to the Baader.
                          > > > >
                          > > > > Thanks,
                          > > > >
                          > > > > Bob
                          > > > >
                          > > > >
                          > > > > -----Original Message-----
                          > > > > From: Don Goldman [mailto:donclearview@y...]
                          > > > > Sent: Thursday, April 01, 2004 3:11 PM
                          > > > > To: ccd-newastro@yahoogroups.com
                          > > > > Subject: [ccd-newastro] Re: question about strange results from
                          > > LPR
                          > > > > filter
                          > > > >
                          > > > > Peter, just spectrally measured the Baader filter here at
                          > work.
                          > > > The
                          > > > > small peaks that you see posted at Adirondack below 400 nm are
                          > > > > there. They amount to only about 4% of a typical blue filter
                          > > > > transmission, and about 1.5% of the Red+Green+Blue. Since the
                          > > CCD
                          > > > > QE drops off so strongly below about 420 nm, these peaks will
                          > not
                          > > > > have much of an effect. I think this is an excellent low-cost
                          > > > filter
                          > > > > for the web-cams.
                          > > > >
                          > > > > Don Goldman
                          > > > > www.astrodon.com
                          > > > >
                          > > > >
                          > > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...>
                          > > > wrote:
                          > > > > > The curve that I was referring to was the one on the
                          > Adirondack
                          > > > web
                          > > > > > site. There, below the sharp cut-off at 400nm, is another
                          > peak
                          > > > > > extending down to nearly 300nm. Did the curve that came with
                          > > your
                          > > > > > filter extend the data down to 300nm? Certainly moving the
                          > cut-
                          > > > off
                          > > > > to
                          > > > > > 430nm eats into the blue flux, but unfortunately that seems
                          > to
                          > > be
                          > > > > > where any APOs that I've seen data on start to become
                          > > diffraction
                          > > > > > limited (hence the blue halos otherwise).
                          > > > > >
                          > > > > > Peter
                          > > > > >
                          > > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                          > > > > <donclearview@y...>
                          > > > > > wrote:
                          > > > > > > Peter, the scan that came with the Baadar showed very sharp
                          > > > > cutoffs
                          > > > > > > at 400 and 700 nm with the UV and NIR blocked.
                          > > > > > >
                          > > > > > > I find it hard to accept your premise about a filter that
                          > > > blocks
                          > > > > up
                          > > > > > > to 430 nm. That does not leave much in the blue spectral
                          > > > region,
                          > > > > > > although it will certainly remove blue halos in refractors,
                          > > as
                          > > > > does
                          > > > > > > the minus violet filter from Lumicon.
                          > > > > > >
                          > > > > > > Don Goldman
                          > > > > > > www.astrodon.com
                          > > > > > >
                          > > > > > >
                          > > > > > >
                          > > > > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe"
                          > > <erdmanp@e...>
                          > > > > wrote:
                          > > > > > > > The Baader UV/NIR filter does block NIR, and may be the
                          > > best
                          > > > > filter
                          > > > > > > > available for the purpose. But I remain confused how it
                          > > can
                          > > > be
                          > > > > > > called
                          > > > > > > > a UV blocker when it has appreciable transmission down to
                          > > > nearly
                          > > > > > > > 300nm. At that point atmospheric ozone is the more
                          > > important
                          > > > > > > blocker.
                          > > > > > > >
                          > > > > > > > I'm still waiting for a properly designed UV/NIR blocker
                          > > > > suitable
                          > > > > > > for
                          > > > > > > > APO refractors, tranmission range of 450-850nm where they
                          > > are
                          > > > > mostly
                          > > > > > > > still diffraction limited. Everything presently cuts off
                          > > at
                          > > > > 700nm
                          > > > > > > > (too early, wasting light) and transmits down to below
                          > > 400nm
                          > > > > (much
                          > > > > > > too
                          > > > > > > > far).
                          > > > > > > >
                          > > > > > > > Peter
                          > > > > > > >
                          > > > > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                          > > > > > > <donclearview@y...>
                          > > > > > > > wrote:
                          > > > > > > > > Alex,
                          > > > > > > > >
                          > > > > > > > > The Meade, and I suspect, Celestron LPS filter let near-
                          > > > > infrared
                          > > > > > > > > light pass to the web cam. The Meade LPS blocks UV.
                          > > Don't
                          > > > > have
                          > > > > > > any
                          > > > > > > > > data on the Celestron. The chromatic aberration you're
                          > > > > seeing is
                          > > > > > > > > likely related to this. I saw it in my own web cam.
                          > The
                          > > > > more
                          > > > > > > > > expensive Hutech/IDAS LPS blocks UV and NIR but may not
                          > > > > provide
                          > > > > > > good
                          > > > > > > > > overall color balance for your camera. I think the best
                          > > > > solution
                          > > > > > > is
                          > > > > > > > > to buy the new Baadar UV/NIR cutoff filter for $42. It
                          > > > > solves
                          > > > > > > this
                          > > > > > > > > problem. I bought mine from Alpine Astronomical, but I
                          > > > think
                          > > > > > > > > Adirondack now sells them, too.
                          > > > > > > > >
                          > > > > > > > > Don Goldman
                          > > > > > > > > www.astrodon.com
                          > > > > > > > >
                          > > > > > > > >
                          > > > > > > > > --- In ccd-newastro@yahoogroups.com, "ianderca"
                          > > > > <ianderca@y...>
                          > > > > > > wrote:
                          > > > > > > > > > I have just bought a celestron LPR filter, and I
                          > notice
                          > > a
                          > > > > > > > > remarkable
                          > > > > > > > > > cromatic aberration from my photo with webcam but in
                          > > > visual
                          > > > > > > too:
                          > > > > > > > > the
                          > > > > > > > > > filter produce a red and blu abberration on the
                          > > opposite
                          > > > > side
                          > > > > > > of a
                          > > > > > > > > > star for example, similar but more accentuated than
                          > > > > cromatic
                          > > > > > > > > > aberration from stars at low level hight. This is
                          > > normal?
                          > > > > If
                          > > > > > > yes ,
                          > > > > > > > > > do you mean that you can use this filter only for
                          > > visual
                          > > > > > > > > observation
                          > > > > > > > > > of faint object?
                          > > > > > > > > >
                          > > > > > > > > > please, if someone have any experience about using it
                          > I
                          > > > > would
                          > > > > > > > > > appreciate any information. I wonder if my filter is
                          > > bad.
                          > > > > > > > > >
                          > > > > > > > > > best regards
                          > > > > > > > > > Alex
                          > > > >
                          > > > >
                          > > > >
                          > > > >
                          > > > >
                          > > > > Yahoo! Groups Links
                          > > >
                          > > >
                          > > >
                          > > >
                          > > >
                          > > > Yahoo! Groups Links
                        • Jon Talbot
                          Yep, I agree with your analysis. The better corrected lenses may not need this filter at all. At least if one wants to shoot with a non apo type lens or only
                          Message 12 of 18 , Apr 2, 2004
                          • 0 Attachment
                            Yep,
                            I agree with your analysis. The better corrected lenses may not need
                            this filter at all. At least if one wants to shoot with a non apo
                            type lens or only has that type of system this filter provides for
                            better results than others on the market.

                            Jon Talbot

                            --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                            <donclearview@y...> wrote:
                            > John, Chet Schuler designed this filter for this very reason. For
                            > less corrected scopes, and achromats will certainly be in this
                            group,
                            > the Schuler filter should be much better than the Baader even
                            though
                            > you take a big light hit in the blue filter. It is not surprising
                            > that you needed a much higher weight. So, this is all consistent.
                            > The FSQ and perhaps the NP101 and AP155 may not need such a severe
                            > approach.
                            >
                            > Don Goldman
                            > www.astrodon.com
                            >
                            >
                            > --- In ccd-newastro@yahoogroups.com, "Jon Talbot" <hurricane4@c...>
                            > wrote:
                            > > Don, I use the Schuler filter with my Stellarvue Nighthawk
                            Achromat
                            > > and find it works best in reducing the blue halo's I did a
                            little
                            > > test comparing the Baader Fringe Killer with the Schuler and the
                            > > Schuler won. There wasnt alot of science in this test just
                            visual
                            > > impression. Here is the link.
                            > > http://www.myweb.cableone.net/hurricane4/Filter Test.html
                            > >
                            > > I find I need to weight the blue frame about 2x compared to green
                            > > using the SXV-H9. Here are two images I've taken with the
                            Schuler
                            > > filter. Not too bad for a Achromat!
                            > >
                            > > http://www.myweb.cableone.net/hurricane4/M67_031804.html
                            > > http://www.myweb.cableone.net/hurricane4/M78_012204.html
                            > >
                            > > Jon Talbot
                            > >
                            > >
                            > > --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                            > > wrote:
                            > > > Hi Don:
                            > > >
                            > > > You might find this interesting.
                            > > >
                            > > > Here is a before and after of M31 from my Tak FS60C, with and
                            > > without
                            > > > the Schuler filter. Please pardon the magenta cast to the
                            images
                            > as
                            > > they
                            > > > were done before I calibrated my monitor with a Spyder. I
                            > certainly
                            > > need
                            > > > to go back and fix them <g>.
                            > > >
                            > > > No filter: http://www.bobholzer.com/m31fs60cfinal.jpg
                            > > > Filter: http://www.bobholzer.com/m31lrgbfs60c.jpg
                            > > >
                            > > > Big difference, eh? My Tak FSQ-106 certainly doesn't need the
                            > filter
                            > > > either.
                            > > >
                            > > > BTW, if you would like to borrow this filter to test, let me
                            > know. I
                            > > > have 2 of them. Or if you would like one, would you take a
                            > partial
                            > > trade
                            > > > for one of your Ha filters <g>? Besides, it's galaxy season so
                            > the
                            > > wide
                            > > > field FS60C is not seeing any light.
                            > > >
                            > > > Bob
                            > > >
                            > > >
                            > > >
                            > > >
                            > > >
                            > > > -----Original Message-----
                            > > > From: Don Goldman [mailto:donclearview@y...]
                            > > > Sent: Thursday, April 01, 2004 7:13 PM
                            > > > To: ccd-newastro@yahoogroups.com
                            > > > Subject: [ccd-newastro] Re: question about strange results from
                            > LPR
                            > > > filter
                            > > >
                            > > > > Bob
                            > > >
                            > > > For some reason this didn't post. I'm resending it now. If it
                            > > appears
                            > > > twice, sorry about that!
                            > > >
                            > > > I didn't know about the Schuler "Not V (=violet) and IR
                            filter",
                            > > but
                            > > > did a little research. I see Anacortes sells it. No curves
                            > > > published, but.........I have my ways. It gradually cuts on
                            > where
                            > > it
                            > > > transmits about 50% at 430 nm and then slowly tails down in the
                            > NIR
                            > > > similar to the Schuler red and luminance filters that I have
                            > > plotted
                            > > > on my web site. This eliminates the blue halos and fringing in
                            > the
                            > > > less expensive refractors and would be perfect for the web
                            cams,
                            > > > likely better than the Baader filter. Peter was right. 400 nm
                            is
                            > > too
                            > > > early to cut out fringing in some of the lower cost
                            refractors.
                            > > > That's why Lumicon came out with the -violet filter some time
                            > > ago.
                            > > > For CCD imaging, the blue filter will take a hard hit and you
                            > will
                            > > > likely have to weight it ~3x compared to green. I think I have
                            > > been
                            > > > unknowingly biased, since my TAK FSQ is so incredibly corrected
                            > > that
                            > > > I don't see the problems that people see in less expensive
                            > > > refractors. Hope this helps and thanks for getting me to dig
                            > > around
                            > > > and find out more about this Schuler filter.
                            > > >
                            > > > Don Goldman
                            > > > www.astrodon.com
                            > > >
                            > > >
                            > > >
                            > > >
                            > > > --- In ccd-newastro@yahoogroups.com, "Bob Holzer"
                            <b.holzer@c...>
                            > > > wrote:
                            > > > > Don:
                            > > > >
                            > > > > By any chance have you measured Schuler's Not IR/UV filter?
                            > I've
                            > > > been
                            > > > > using it to cut blue bloat on my Tak FS60C with great
                            results,
                            > > but
                            > > > just
                            > > > > wonder how the numbers actually compare to the Baader.
                            > > > >
                            > > > > Thanks,
                            > > > >
                            > > > > Bob
                            > > > >
                            > > > >
                            > > > > -----Original Message-----
                            > > > > From: Don Goldman [mailto:donclearview@y...]
                            > > > > Sent: Thursday, April 01, 2004 3:11 PM
                            > > > > To: ccd-newastro@yahoogroups.com
                            > > > > Subject: [ccd-newastro] Re: question about strange results
                            from
                            > > LPR
                            > > > > filter
                            > > > >
                            > > > > Peter, just spectrally measured the Baader filter here at
                            > work.
                            > > > The
                            > > > > small peaks that you see posted at Adirondack below 400 nm
                            are
                            > > > > there. They amount to only about 4% of a typical blue filter
                            > > > > transmission, and about 1.5% of the Red+Green+Blue. Since
                            the
                            > > CCD
                            > > > > QE drops off so strongly below about 420 nm, these peaks will
                            > not
                            > > > > have much of an effect. I think this is an excellent low-cost
                            > > > filter
                            > > > > for the web-cams.
                            > > > >
                            > > > > Don Goldman
                            > > > > www.astrodon.com
                            > > > >
                            > > > >
                            > > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe"
                            <erdmanp@e...>
                            > > > wrote:
                            > > > > > The curve that I was referring to was the one on the
                            > Adirondack
                            > > > web
                            > > > > > site. There, below the sharp cut-off at 400nm, is another
                            > peak
                            > > > > > extending down to nearly 300nm. Did the curve that came
                            with
                            > > your
                            > > > > > filter extend the data down to 300nm? Certainly moving the
                            > cut-
                            > > > off
                            > > > > to
                            > > > > > 430nm eats into the blue flux, but unfortunately that seems
                            > to
                            > > be
                            > > > > > where any APOs that I've seen data on start to become
                            > > diffraction
                            > > > > > limited (hence the blue halos otherwise).
                            > > > > >
                            > > > > > Peter
                            > > > > >
                            > > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                            > > > > <donclearview@y...>
                            > > > > > wrote:
                            > > > > > > Peter, the scan that came with the Baadar showed very
                            sharp
                            > > > > cutoffs
                            > > > > > > at 400 and 700 nm with the UV and NIR blocked.
                            > > > > > >
                            > > > > > > I find it hard to accept your premise about a filter that
                            > > > blocks
                            > > > > up
                            > > > > > > to 430 nm. That does not leave much in the blue spectral
                            > > > region,
                            > > > > > > although it will certainly remove blue halos in
                            refractors,
                            > > as
                            > > > > does
                            > > > > > > the minus violet filter from Lumicon.
                            > > > > > >
                            > > > > > > Don Goldman
                            > > > > > > www.astrodon.com
                            > > > > > >
                            > > > > > >
                            > > > > > >
                            > > > > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe"
                            > > <erdmanp@e...>
                            > > > > wrote:
                            > > > > > > > The Baader UV/NIR filter does block NIR, and may be the
                            > > best
                            > > > > filter
                            > > > > > > > available for the purpose. But I remain confused how
                            it
                            > > can
                            > > > be
                            > > > > > > called
                            > > > > > > > a UV blocker when it has appreciable transmission down
                            to
                            > > > nearly
                            > > > > > > > 300nm. At that point atmospheric ozone is the more
                            > > important
                            > > > > > > blocker.
                            > > > > > > >
                            > > > > > > > I'm still waiting for a properly designed UV/NIR
                            blocker
                            > > > > suitable
                            > > > > > > for
                            > > > > > > > APO refractors, tranmission range of 450-850nm where
                            they
                            > > are
                            > > > > mostly
                            > > > > > > > still diffraction limited. Everything presently cuts
                            off
                            > > at
                            > > > > 700nm
                            > > > > > > > (too early, wasting light) and transmits down to below
                            > > 400nm
                            > > > > (much
                            > > > > > > too
                            > > > > > > > far).
                            > > > > > > >
                            > > > > > > > Peter
                            > > > > > > >
                            > > > > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                            > > > > > > <donclearview@y...>
                            > > > > > > > wrote:
                            > > > > > > > > Alex,
                            > > > > > > > >
                            > > > > > > > > The Meade, and I suspect, Celestron LPS filter let
                            near-
                            > > > > infrared
                            > > > > > > > > light pass to the web cam. The Meade LPS blocks UV.
                            > > Don't
                            > > > > have
                            > > > > > > any
                            > > > > > > > > data on the Celestron. The chromatic aberration
                            you're
                            > > > > seeing is
                            > > > > > > > > likely related to this. I saw it in my own web cam.
                            > The
                            > > > > more
                            > > > > > > > > expensive Hutech/IDAS LPS blocks UV and NIR but may
                            not
                            > > > > provide
                            > > > > > > good
                            > > > > > > > > overall color balance for your camera. I think the
                            best
                            > > > > solution
                            > > > > > > is
                            > > > > > > > > to buy the new Baadar UV/NIR cutoff filter for $42.
                            It
                            > > > > solves
                            > > > > > > this
                            > > > > > > > > problem. I bought mine from Alpine Astronomical, but
                            I
                            > > > think
                            > > > > > > > > Adirondack now sells them, too.
                            > > > > > > > >
                            > > > > > > > > Don Goldman
                            > > > > > > > > www.astrodon.com
                            > > > > > > > >
                            > > > > > > > >
                            > > > > > > > > --- In ccd-newastro@yahoogroups.com, "ianderca"
                            > > > > <ianderca@y...>
                            > > > > > > wrote:
                            > > > > > > > > > I have just bought a celestron LPR filter, and I
                            > notice
                            > > a
                            > > > > > > > > remarkable
                            > > > > > > > > > cromatic aberration from my photo with webcam but
                            in
                            > > > visual
                            > > > > > > too:
                            > > > > > > > > the
                            > > > > > > > > > filter produce a red and blu abberration on the
                            > > opposite
                            > > > > side
                            > > > > > > of a
                            > > > > > > > > > star for example, similar but more accentuated
                            than
                            > > > > cromatic
                            > > > > > > > > > aberration from stars at low level hight. This is
                            > > normal?
                            > > > > If
                            > > > > > > yes ,
                            > > > > > > > > > do you mean that you can use this filter only for
                            > > visual
                            > > > > > > > > observation
                            > > > > > > > > > of faint object?
                            > > > > > > > > >
                            > > > > > > > > > please, if someone have any experience about using
                            it
                            > I
                            > > > > would
                            > > > > > > > > > appreciate any information. I wonder if my filter
                            is
                            > > bad.
                            > > > > > > > > >
                            > > > > > > > > > best regards
                            > > > > > > > > > Alex
                            > > > >
                            > > > >
                            > > > >
                            > > > >
                            > > > >
                            > > > > Yahoo! Groups Links
                            > > >
                            > > >
                            > > >
                            > > >
                            > > >
                            > > > Yahoo! Groups Links
                          • Wodaski Yahoo
                            Not UV - IR. I found I could get a slight reduction in star size on the FSQ with an IR blocking filter. Around 10-15% smaller. Not a huge difference, but worth
                            Message 13 of 18 , Apr 2, 2004
                            • 0 Attachment
                              Not UV - IR. I found I could get a slight reduction in star size on the FSQ
                              with an IR blocking filter. Around 10-15% smaller. Not a huge difference,
                              but worth noting.


                              Ron Wodaski
                              The New CCD Astronomy
                              http://www.newastro.com/ipb

                              -----Original Message-----
                              From: erdmanpe [mailto:erdmanp@...]
                              Sent: Friday, April 02, 2004 8:22 PM
                              To: ccd-newastro@yahoogroups.com
                              Subject: [ccd-newastro] Re: question about strange results from LPR filter

                              It would be fine if I were corrected, but didn't Wodaski have a web
                              page on reducing blue bloat in an FSQ with a UV reject filter? The
                              only reason I might remember it is because I was so surprised it might
                              need such a filter.

                              Peter

                              --- In ccd-newastro@yahoogroups.com, "Don Goldman" <donclearview@y...>
                              wrote:
                              > John, Chet Schuler designed this filter for this very reason. For
                              > less corrected scopes, and achromats will certainly be in this group,
                              > the Schuler filter should be much better than the Baader even though
                              > you take a big light hit in the blue filter. It is not surprising
                              > that you needed a much higher weight. So, this is all consistent.
                              > The FSQ and perhaps the NP101 and AP155 may not need such a severe
                              > approach.
                              >
                              > Don Goldman
                              > www.astrodon.com
                              >
                              >
                              > --- In ccd-newastro@yahoogroups.com, "Jon Talbot" <hurricane4@c...>
                              > wrote:
                              > > Don, I use the Schuler filter with my Stellarvue Nighthawk Achromat
                              > > and find it works best in reducing the blue halo's I did a little
                              > > test comparing the Baader Fringe Killer with the Schuler and the
                              > > Schuler won. There wasnt alot of science in this test just visual
                              > > impression. Here is the link.
                              > > http://www.myweb.cableone.net/hurricane4/Filter Test.html
                              > >
                              > > I find I need to weight the blue frame about 2x compared to green
                              > > using the SXV-H9. Here are two images I've taken with the Schuler
                              > > filter. Not too bad for a Achromat!
                              > >
                              > > http://www.myweb.cableone.net/hurricane4/M67_031804.html
                              > > http://www.myweb.cableone.net/hurricane4/M78_012204.html
                              > >
                              > > Jon Talbot
                              > >
                              > >
                              > > --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                              > > wrote:
                              > > > Hi Don:
                              > > >
                              > > > You might find this interesting.
                              > > >
                              > > > Here is a before and after of M31 from my Tak FS60C, with and
                              > > without
                              > > > the Schuler filter. Please pardon the magenta cast to the images
                              > as
                              > > they
                              > > > were done before I calibrated my monitor with a Spyder. I
                              > certainly
                              > > need
                              > > > to go back and fix them <g>.
                              > > >
                              > > > No filter: http://www.bobholzer.com/m31fs60cfinal.jpg
                              > > > Filter: http://www.bobholzer.com/m31lrgbfs60c.jpg
                              > > >
                              > > > Big difference, eh? My Tak FSQ-106 certainly doesn't need the
                              > filter
                              > > > either.
                              > > >
                              > > > BTW, if you would like to borrow this filter to test, let me
                              > know. I
                              > > > have 2 of them. Or if you would like one, would you take a
                              > partial
                              > > trade
                              > > > for one of your Ha filters <g>? Besides, it's galaxy season so
                              > the
                              > > wide
                              > > > field FS60C is not seeing any light.
                              > > >
                              > > > Bob
                              > > >
                              > > >
                              > > >
                              > > >
                              > > >
                              > > > -----Original Message-----
                              > > > From: Don Goldman [mailto:donclearview@y...]
                              > > > Sent: Thursday, April 01, 2004 7:13 PM
                              > > > To: ccd-newastro@yahoogroups.com
                              > > > Subject: [ccd-newastro] Re: question about strange results from
                              > LPR
                              > > > filter
                              > > >
                              > > > > Bob
                              > > >
                              > > > For some reason this didn't post. I'm resending it now. If it
                              > > appears
                              > > > twice, sorry about that!
                              > > >
                              > > > I didn't know about the Schuler "Not V (=violet) and IR filter",
                              > > but
                              > > > did a little research. I see Anacortes sells it. No curves
                              > > > published, but.........I have my ways. It gradually cuts on
                              > where
                              > > it
                              > > > transmits about 50% at 430 nm and then slowly tails down in the
                              > NIR
                              > > > similar to the Schuler red and luminance filters that I have
                              > > plotted
                              > > > on my web site. This eliminates the blue halos and fringing in
                              > the
                              > > > less expensive refractors and would be perfect for the web cams,
                              > > > likely better than the Baader filter. Peter was right. 400 nm is
                              > > too
                              > > > early to cut out fringing in some of the lower cost refractors.
                              > > > That's why Lumicon came out with the -violet filter some time
                              > > ago.
                              > > > For CCD imaging, the blue filter will take a hard hit and you
                              > will
                              > > > likely have to weight it ~3x compared to green. I think I have
                              > > been
                              > > > unknowingly biased, since my TAK FSQ is so incredibly corrected
                              > > that
                              > > > I don't see the problems that people see in less expensive
                              > > > refractors. Hope this helps and thanks for getting me to dig
                              > > around
                              > > > and find out more about this Schuler filter.
                              > > >
                              > > > Don Goldman
                              > > > www.astrodon.com
                              > > >
                              > > >
                              > > >
                              > > >
                              > > > --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                              > > > wrote:
                              > > > > Don:
                              > > > >
                              > > > > By any chance have you measured Schuler's Not IR/UV filter?
                              > I've
                              > > > been
                              > > > > using it to cut blue bloat on my Tak FS60C with great results,
                              > > but
                              > > > just
                              > > > > wonder how the numbers actually compare to the Baader.
                              > > > >
                              > > > > Thanks,
                              > > > >
                              > > > > Bob
                              > > > >
                              > > > >
                              > > > > -----Original Message-----
                              > > > > From: Don Goldman [mailto:donclearview@y...]
                              > > > > Sent: Thursday, April 01, 2004 3:11 PM
                              > > > > To: ccd-newastro@yahoogroups.com
                              > > > > Subject: [ccd-newastro] Re: question about strange results from
                              > > LPR
                              > > > > filter
                              > > > >
                              > > > > Peter, just spectrally measured the Baader filter here at
                              > work.
                              > > > The
                              > > > > small peaks that you see posted at Adirondack below 400 nm are
                              > > > > there. They amount to only about 4% of a typical blue filter
                              > > > > transmission, and about 1.5% of the Red+Green+Blue. Since the
                              > > CCD
                              > > > > QE drops off so strongly below about 420 nm, these peaks will
                              > not
                              > > > > have much of an effect. I think this is an excellent low-cost
                              > > > filter
                              > > > > for the web-cams.
                              > > > >
                              > > > > Don Goldman
                              > > > > www.astrodon.com
                              > > > >
                              > > > >
                              > > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...>
                              > > > wrote:
                              > > > > > The curve that I was referring to was the one on the
                              > Adirondack
                              > > > web
                              > > > > > site. There, below the sharp cut-off at 400nm, is another
                              > peak
                              > > > > > extending down to nearly 300nm. Did the curve that came with
                              > > your
                              > > > > > filter extend the data down to 300nm? Certainly moving the
                              > cut-
                              > > > off
                              > > > > to
                              > > > > > 430nm eats into the blue flux, but unfortunately that seems
                              > to
                              > > be
                              > > > > > where any APOs that I've seen data on start to become
                              > > diffraction
                              > > > > > limited (hence the blue halos otherwise).
                              > > > > >
                              > > > > > Peter
                              > > > > >
                              > > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                              > > > > <donclearview@y...>
                              > > > > > wrote:
                              > > > > > > Peter, the scan that came with the Baadar showed very sharp
                              > > > > cutoffs
                              > > > > > > at 400 and 700 nm with the UV and NIR blocked.
                              > > > > > >
                              > > > > > > I find it hard to accept your premise about a filter that
                              > > > blocks
                              > > > > up
                              > > > > > > to 430 nm. That does not leave much in the blue spectral
                              > > > region,
                              > > > > > > although it will certainly remove blue halos in refractors,
                              > > as
                              > > > > does
                              > > > > > > the minus violet filter from Lumicon.
                              > > > > > >
                              > > > > > > Don Goldman
                              > > > > > > www.astrodon.com
                              > > > > > >
                              > > > > > >
                              > > > > > >
                              > > > > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe"
                              > > <erdmanp@e...>
                              > > > > wrote:
                              > > > > > > > The Baader UV/NIR filter does block NIR, and may be the
                              > > best
                              > > > > filter
                              > > > > > > > available for the purpose. But I remain confused how it
                              > > can
                              > > > be
                              > > > > > > called
                              > > > > > > > a UV blocker when it has appreciable transmission down to
                              > > > nearly
                              > > > > > > > 300nm. At that point atmospheric ozone is the more
                              > > important
                              > > > > > > blocker.
                              > > > > > > >
                              > > > > > > > I'm still waiting for a properly designed UV/NIR blocker
                              > > > > suitable
                              > > > > > > for
                              > > > > > > > APO refractors, tranmission range of 450-850nm where they
                              > > are
                              > > > > mostly
                              > > > > > > > still diffraction limited. Everything presently cuts off
                              > > at
                              > > > > 700nm
                              > > > > > > > (too early, wasting light) and transmits down to below
                              > > 400nm
                              > > > > (much
                              > > > > > > too
                              > > > > > > > far).
                              > > > > > > >
                              > > > > > > > Peter
                              > > > > > > >
                              > > > > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                              > > > > > > <donclearview@y...>
                              > > > > > > > wrote:
                              > > > > > > > > Alex,
                              > > > > > > > >
                              > > > > > > > > The Meade, and I suspect, Celestron LPS filter let near-
                              > > > > infrared
                              > > > > > > > > light pass to the web cam. The Meade LPS blocks UV.
                              > > Don't
                              > > > > have
                              > > > > > > any
                              > > > > > > > > data on the Celestron. The chromatic aberration you're
                              > > > > seeing is
                              > > > > > > > > likely related to this. I saw it in my own web cam.
                              > The
                              > > > > more
                              > > > > > > > > expensive Hutech/IDAS LPS blocks UV and NIR but may not
                              > > > > provide
                              > > > > > > good
                              > > > > > > > > overall color balance for your camera. I think the best
                              > > > > solution
                              > > > > > > is
                              > > > > > > > > to buy the new Baadar UV/NIR cutoff filter for $42. It
                              > > > > solves
                              > > > > > > this
                              > > > > > > > > problem. I bought mine from Alpine Astronomical, but I
                              > > > think
                              > > > > > > > > Adirondack now sells them, too.
                              > > > > > > > >
                              > > > > > > > > Don Goldman
                              > > > > > > > > www.astrodon.com
                              > > > > > > > >
                              > > > > > > > >
                              > > > > > > > > --- In ccd-newastro@yahoogroups.com, "ianderca"
                              > > > > <ianderca@y...>
                              > > > > > > wrote:
                              > > > > > > > > > I have just bought a celestron LPR filter, and I
                              > notice
                              > > a
                              > > > > > > > > remarkable
                              > > > > > > > > > cromatic aberration from my photo with webcam but in
                              > > > visual
                              > > > > > > too:
                              > > > > > > > > the
                              > > > > > > > > > filter produce a red and blu abberration on the
                              > > opposite
                              > > > > side
                              > > > > > > of a
                              > > > > > > > > > star for example, similar but more accentuated than
                              > > > > cromatic
                              > > > > > > > > > aberration from stars at low level hight. This is
                              > > normal?
                              > > > > If
                              > > > > > > yes ,
                              > > > > > > > > > do you mean that you can use this filter only for
                              > > visual
                              > > > > > > > > observation
                              > > > > > > > > > of faint object?
                              > > > > > > > > >
                              > > > > > > > > > please, if someone have any experience about using it
                              > I
                              > > > > would
                              > > > > > > > > > appreciate any information. I wonder if my filter is
                              > > bad.
                              > > > > > > > > >
                              > > > > > > > > > best regards
                              > > > > > > > > > Alex
                              > > > >
                              > > > >
                              > > > >
                              > > > >
                              > > > >
                              > > > > Yahoo! Groups Links
                              > > >
                              > > >
                              > > >
                              > > >
                              > > >
                              > > > Yahoo! Groups Links






                              Yahoo! Groups Links
                            • erdmanpe
                              Ah!, I couldn t quite remember which end of the useful spectrum. Where did your filter cut off to get the improved star sizes? Peter ... the FSQ ...
                              Message 14 of 18 , Apr 2, 2004
                              • 0 Attachment
                                Ah!, I couldn't quite remember which end of the useful spectrum.
                                Where did your filter cut off to get the improved star sizes?

                                Peter

                                --- In ccd-newastro@yahoogroups.com, "Wodaski Yahoo" <yahoo@n...> wrote:
                                > Not UV - IR. I found I could get a slight reduction in star size on
                                the FSQ
                                > with an IR blocking filter. Around 10-15% smaller. Not a huge
                                difference,
                                > but worth noting.
                                >
                                >
                                > Ron Wodaski
                                > The New CCD Astronomy
                                > http://www.newastro.com/ipb
                                >
                                > -----Original Message-----
                                > From: erdmanpe [mailto:erdmanp@e...]
                                > Sent: Friday, April 02, 2004 8:22 PM
                                > To: ccd-newastro@yahoogroups.com
                                > Subject: [ccd-newastro] Re: question about strange results from LPR
                                filter
                                >
                                > It would be fine if I were corrected, but didn't Wodaski have a web
                                > page on reducing blue bloat in an FSQ with a UV reject filter? The
                                > only reason I might remember it is because I was so surprised it might
                                > need such a filter.
                                >
                                > Peter
                                >
                                > --- In ccd-newastro@yahoogroups.com, "Don Goldman" <donclearview@y...>
                                > wrote:
                                > > John, Chet Schuler designed this filter for this very reason. For
                                > > less corrected scopes, and achromats will certainly be in this group,
                                > > the Schuler filter should be much better than the Baader even though
                                > > you take a big light hit in the blue filter. It is not surprising
                                > > that you needed a much higher weight. So, this is all consistent.
                                > > The FSQ and perhaps the NP101 and AP155 may not need such a severe
                                > > approach.
                                > >
                                > > Don Goldman
                                > > www.astrodon.com
                                > >
                                > >
                                > > --- In ccd-newastro@yahoogroups.com, "Jon Talbot" <hurricane4@c...>
                                > > wrote:
                                > > > Don, I use the Schuler filter with my Stellarvue Nighthawk Achromat
                                > > > and find it works best in reducing the blue halo's I did a little
                                > > > test comparing the Baader Fringe Killer with the Schuler and the
                                > > > Schuler won. There wasnt alot of science in this test just visual
                                > > > impression. Here is the link.
                                > > > http://www.myweb.cableone.net/hurricane4/Filter Test.html
                                > > >
                                > > > I find I need to weight the blue frame about 2x compared to green
                                > > > using the SXV-H9. Here are two images I've taken with the Schuler
                                > > > filter. Not too bad for a Achromat!
                                > > >
                                > > > http://www.myweb.cableone.net/hurricane4/M67_031804.html
                                > > > http://www.myweb.cableone.net/hurricane4/M78_012204.html
                                > > >
                                > > > Jon Talbot
                                > > >
                                > > >
                                > > > --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                                > > > wrote:
                                > > > > Hi Don:
                                > > > >
                                > > > > You might find this interesting.
                                > > > >
                                > > > > Here is a before and after of M31 from my Tak FS60C, with and
                                > > > without
                                > > > > the Schuler filter. Please pardon the magenta cast to the images
                                > > as
                                > > > they
                                > > > > were done before I calibrated my monitor with a Spyder. I
                                > > certainly
                                > > > need
                                > > > > to go back and fix them <g>.
                                > > > >
                                > > > > No filter: http://www.bobholzer.com/m31fs60cfinal.jpg
                                > > > > Filter: http://www.bobholzer.com/m31lrgbfs60c.jpg
                                > > > >
                                > > > > Big difference, eh? My Tak FSQ-106 certainly doesn't need the
                                > > filter
                                > > > > either.
                                > > > >
                                > > > > BTW, if you would like to borrow this filter to test, let me
                                > > know. I
                                > > > > have 2 of them. Or if you would like one, would you take a
                                > > partial
                                > > > trade
                                > > > > for one of your Ha filters <g>? Besides, it's galaxy season so
                                > > the
                                > > > wide
                                > > > > field FS60C is not seeing any light.
                                > > > >
                                > > > > Bob
                                > > > >
                                > > > >
                                > > > >
                                > > > >
                                > > > >
                                > > > > -----Original Message-----
                                > > > > From: Don Goldman [mailto:donclearview@y...]
                                > > > > Sent: Thursday, April 01, 2004 7:13 PM
                                > > > > To: ccd-newastro@yahoogroups.com
                                > > > > Subject: [ccd-newastro] Re: question about strange results from
                                > > LPR
                                > > > > filter
                                > > > >
                                > > > > > Bob
                                > > > >
                                > > > > For some reason this didn't post. I'm resending it now. If it
                                > > > appears
                                > > > > twice, sorry about that!
                                > > > >
                                > > > > I didn't know about the Schuler "Not V (=violet) and IR filter",
                                > > > but
                                > > > > did a little research. I see Anacortes sells it. No curves
                                > > > > published, but.........I have my ways. It gradually cuts on
                                > > where
                                > > > it
                                > > > > transmits about 50% at 430 nm and then slowly tails down in the
                                > > NIR
                                > > > > similar to the Schuler red and luminance filters that I have
                                > > > plotted
                                > > > > on my web site. This eliminates the blue halos and fringing in
                                > > the
                                > > > > less expensive refractors and would be perfect for the web cams,
                                > > > > likely better than the Baader filter. Peter was right. 400 nm is
                                > > > too
                                > > > > early to cut out fringing in some of the lower cost refractors.
                                > > > > That's why Lumicon came out with the -violet filter some time
                                > > > ago.
                                > > > > For CCD imaging, the blue filter will take a hard hit and you
                                > > will
                                > > > > likely have to weight it ~3x compared to green. I think I have
                                > > > been
                                > > > > unknowingly biased, since my TAK FSQ is so incredibly corrected
                                > > > that
                                > > > > I don't see the problems that people see in less expensive
                                > > > > refractors. Hope this helps and thanks for getting me to dig
                                > > > around
                                > > > > and find out more about this Schuler filter.
                                > > > >
                                > > > > Don Goldman
                                > > > > www.astrodon.com
                                > > > >
                                > > > >
                                > > > >
                                > > > >
                                > > > > --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                                > > > > wrote:
                                > > > > > Don:
                                > > > > >
                                > > > > > By any chance have you measured Schuler's Not IR/UV filter?
                                > > I've
                                > > > > been
                                > > > > > using it to cut blue bloat on my Tak FS60C with great results,
                                > > > but
                                > > > > just
                                > > > > > wonder how the numbers actually compare to the Baader.
                                > > > > >
                                > > > > > Thanks,
                                > > > > >
                                > > > > > Bob
                                > > > > >
                                > > > > >
                                > > > > > -----Original Message-----
                                > > > > > From: Don Goldman [mailto:donclearview@y...]
                                > > > > > Sent: Thursday, April 01, 2004 3:11 PM
                                > > > > > To: ccd-newastro@yahoogroups.com
                                > > > > > Subject: [ccd-newastro] Re: question about strange results from
                                > > > LPR
                                > > > > > filter
                                > > > > >
                                > > > > > Peter, just spectrally measured the Baader filter here at
                                > > work.
                                > > > > The
                                > > > > > small peaks that you see posted at Adirondack below 400 nm are
                                > > > > > there. They amount to only about 4% of a typical blue filter
                                > > > > > transmission, and about 1.5% of the Red+Green+Blue. Since the
                                > > > CCD
                                > > > > > QE drops off so strongly below about 420 nm, these peaks will
                                > > not
                                > > > > > have much of an effect. I think this is an excellent low-cost
                                > > > > filter
                                > > > > > for the web-cams.
                                > > > > >
                                > > > > > Don Goldman
                                > > > > > www.astrodon.com
                                > > > > >
                                > > > > >
                                > > > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...>
                                > > > > wrote:
                                > > > > > > The curve that I was referring to was the one on the
                                > > Adirondack
                                > > > > web
                                > > > > > > site. There, below the sharp cut-off at 400nm, is another
                                > > peak
                                > > > > > > extending down to nearly 300nm. Did the curve that came with
                                > > > your
                                > > > > > > filter extend the data down to 300nm? Certainly moving the
                                > > cut-
                                > > > > off
                                > > > > > to
                                > > > > > > 430nm eats into the blue flux, but unfortunately that seems
                                > > to
                                > > > be
                                > > > > > > where any APOs that I've seen data on start to become
                                > > > diffraction
                                > > > > > > limited (hence the blue halos otherwise).
                                > > > > > >
                                > > > > > > Peter
                                > > > > > >
                                > > > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                                > > > > > <donclearview@y...>
                                > > > > > > wrote:
                                > > > > > > > Peter, the scan that came with the Baadar showed very sharp
                                > > > > > cutoffs
                                > > > > > > > at 400 and 700 nm with the UV and NIR blocked.
                                > > > > > > >
                                > > > > > > > I find it hard to accept your premise about a filter that
                                > > > > blocks
                                > > > > > up
                                > > > > > > > to 430 nm. That does not leave much in the blue spectral
                                > > > > region,
                                > > > > > > > although it will certainly remove blue halos in refractors,
                                > > > as
                                > > > > > does
                                > > > > > > > the minus violet filter from Lumicon.
                                > > > > > > >
                                > > > > > > > Don Goldman
                                > > > > > > > www.astrodon.com
                                > > > > > > >
                                > > > > > > >
                                > > > > > > >
                                > > > > > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe"
                                > > > <erdmanp@e...>
                                > > > > > wrote:
                                > > > > > > > > The Baader UV/NIR filter does block NIR, and may be the
                                > > > best
                                > > > > > filter
                                > > > > > > > > available for the purpose. But I remain confused how it
                                > > > can
                                > > > > be
                                > > > > > > > called
                                > > > > > > > > a UV blocker when it has appreciable transmission down to
                                > > > > nearly
                                > > > > > > > > 300nm. At that point atmospheric ozone is the more
                                > > > important
                                > > > > > > > blocker.
                                > > > > > > > >
                                > > > > > > > > I'm still waiting for a properly designed UV/NIR blocker
                                > > > > > suitable
                                > > > > > > > for
                                > > > > > > > > APO refractors, tranmission range of 450-850nm where they
                                > > > are
                                > > > > > mostly
                                > > > > > > > > still diffraction limited. Everything presently cuts off
                                > > > at
                                > > > > > 700nm
                                > > > > > > > > (too early, wasting light) and transmits down to below
                                > > > 400nm
                                > > > > > (much
                                > > > > > > > too
                                > > > > > > > > far).
                                > > > > > > > >
                                > > > > > > > > Peter
                                > > > > > > > >
                                > > > > > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                                > > > > > > > <donclearview@y...>
                                > > > > > > > > wrote:
                                > > > > > > > > > Alex,
                                > > > > > > > > >
                                > > > > > > > > > The Meade, and I suspect, Celestron LPS filter let near-
                                > > > > > infrared
                                > > > > > > > > > light pass to the web cam. The Meade LPS blocks UV.
                                > > > Don't
                                > > > > > have
                                > > > > > > > any
                                > > > > > > > > > data on the Celestron. The chromatic aberration you're
                                > > > > > seeing is
                                > > > > > > > > > likely related to this. I saw it in my own web cam.
                                > > The
                                > > > > > more
                                > > > > > > > > > expensive Hutech/IDAS LPS blocks UV and NIR but may not
                                > > > > > provide
                                > > > > > > > good
                                > > > > > > > > > overall color balance for your camera. I think the best
                                > > > > > solution
                                > > > > > > > is
                                > > > > > > > > > to buy the new Baadar UV/NIR cutoff filter for $42. It
                                > > > > > solves
                                > > > > > > > this
                                > > > > > > > > > problem. I bought mine from Alpine Astronomical, but I
                                > > > > think
                                > > > > > > > > > Adirondack now sells them, too.
                                > > > > > > > > >
                                > > > > > > > > > Don Goldman
                                > > > > > > > > > www.astrodon.com
                                > > > > > > > > >
                                > > > > > > > > >
                                > > > > > > > > > --- In ccd-newastro@yahoogroups.com, "ianderca"
                                > > > > > <ianderca@y...>
                                > > > > > > > wrote:
                                > > > > > > > > > > I have just bought a celestron LPR filter, and I
                                > > notice
                                > > > a
                                > > > > > > > > > remarkable
                                > > > > > > > > > > cromatic aberration from my photo with webcam but in
                                > > > > visual
                                > > > > > > > too:
                                > > > > > > > > > the
                                > > > > > > > > > > filter produce a red and blu abberration on the
                                > > > opposite
                                > > > > > side
                                > > > > > > > of a
                                > > > > > > > > > > star for example, similar but more accentuated than
                                > > > > > cromatic
                                > > > > > > > > > > aberration from stars at low level hight. This is
                                > > > normal?
                                > > > > > If
                                > > > > > > > yes ,
                                > > > > > > > > > > do you mean that you can use this filter only for
                                > > > visual
                                > > > > > > > > > observation
                                > > > > > > > > > > of faint object?
                                > > > > > > > > > >
                                > > > > > > > > > > please, if someone have any experience about using it
                                > > I
                                > > > > > would
                                > > > > > > > > > > appreciate any information. I wonder if my filter is
                                > > > bad.
                                > > > > > > > > > >
                                > > > > > > > > > > best regards
                                > > > > > > > > > > Alex
                                > > > > >
                                > > > > >
                                > > > > >
                                > > > > >
                                > > > > >
                                > > > > > Yahoo! Groups Links
                                > > > >
                                > > > >
                                > > > >
                                > > > >
                                > > > >
                                > > > > Yahoo! Groups Links
                                >
                                >
                                >
                                >
                                >
                                >
                                > Yahoo! Groups Links
                              • Wodaski Yahoo
                                I don t know. This was years ago, and I just put a handy IR filter on. Don t have those any more; IR blocking is readily available now. Ron Wodaski The New CCD
                                Message 15 of 18 , Apr 2, 2004
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                                  I don't know. This was years ago, and I just put a handy IR filter on. Don't
                                  have those any more; IR blocking is readily available now.


                                  Ron Wodaski
                                  The New CCD Astronomy
                                  http://www.newastro.com/ipb

                                  -----Original Message-----
                                  From: erdmanpe [mailto:erdmanp@...]
                                  Sent: Friday, April 02, 2004 8:55 PM
                                  To: ccd-newastro@yahoogroups.com
                                  Subject: [ccd-newastro] Re: question about strange results from LPR filter

                                  Ah!, I couldn't quite remember which end of the useful spectrum.
                                  Where did your filter cut off to get the improved star sizes?

                                  Peter

                                  --- In ccd-newastro@yahoogroups.com, "Wodaski Yahoo" <yahoo@n...> wrote:
                                  > Not UV - IR. I found I could get a slight reduction in star size on
                                  the FSQ
                                  > with an IR blocking filter. Around 10-15% smaller. Not a huge
                                  difference,
                                  > but worth noting.
                                  >
                                  >
                                  > Ron Wodaski
                                  > The New CCD Astronomy
                                  > http://www.newastro.com/ipb
                                  >
                                  > -----Original Message-----
                                  > From: erdmanpe [mailto:erdmanp@e...]
                                  > Sent: Friday, April 02, 2004 8:22 PM
                                  > To: ccd-newastro@yahoogroups.com
                                  > Subject: [ccd-newastro] Re: question about strange results from LPR
                                  filter
                                  >
                                  > It would be fine if I were corrected, but didn't Wodaski have a web
                                  > page on reducing blue bloat in an FSQ with a UV reject filter? The
                                  > only reason I might remember it is because I was so surprised it might
                                  > need such a filter.
                                  >
                                  > Peter
                                  >
                                  > --- In ccd-newastro@yahoogroups.com, "Don Goldman" <donclearview@y...>
                                  > wrote:
                                  > > John, Chet Schuler designed this filter for this very reason. For
                                  > > less corrected scopes, and achromats will certainly be in this group,
                                  > > the Schuler filter should be much better than the Baader even though
                                  > > you take a big light hit in the blue filter. It is not surprising
                                  > > that you needed a much higher weight. So, this is all consistent.
                                  > > The FSQ and perhaps the NP101 and AP155 may not need such a severe
                                  > > approach.
                                  > >
                                  > > Don Goldman
                                  > > www.astrodon.com
                                  > >
                                  > >
                                  > > --- In ccd-newastro@yahoogroups.com, "Jon Talbot" <hurricane4@c...>
                                  > > wrote:
                                  > > > Don, I use the Schuler filter with my Stellarvue Nighthawk Achromat
                                  > > > and find it works best in reducing the blue halo's I did a little
                                  > > > test comparing the Baader Fringe Killer with the Schuler and the
                                  > > > Schuler won. There wasnt alot of science in this test just visual
                                  > > > impression. Here is the link.
                                  > > > http://www.myweb.cableone.net/hurricane4/Filter Test.html
                                  > > >
                                  > > > I find I need to weight the blue frame about 2x compared to green
                                  > > > using the SXV-H9. Here are two images I've taken with the Schuler
                                  > > > filter. Not too bad for a Achromat!
                                  > > >
                                  > > > http://www.myweb.cableone.net/hurricane4/M67_031804.html
                                  > > > http://www.myweb.cableone.net/hurricane4/M78_012204.html
                                  > > >
                                  > > > Jon Talbot
                                  > > >
                                  > > >
                                  > > > --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                                  > > > wrote:
                                  > > > > Hi Don:
                                  > > > >
                                  > > > > You might find this interesting.
                                  > > > >
                                  > > > > Here is a before and after of M31 from my Tak FS60C, with and
                                  > > > without
                                  > > > > the Schuler filter. Please pardon the magenta cast to the images
                                  > > as
                                  > > > they
                                  > > > > were done before I calibrated my monitor with a Spyder. I
                                  > > certainly
                                  > > > need
                                  > > > > to go back and fix them <g>.
                                  > > > >
                                  > > > > No filter: http://www.bobholzer.com/m31fs60cfinal.jpg
                                  > > > > Filter: http://www.bobholzer.com/m31lrgbfs60c.jpg
                                  > > > >
                                  > > > > Big difference, eh? My Tak FSQ-106 certainly doesn't need the
                                  > > filter
                                  > > > > either.
                                  > > > >
                                  > > > > BTW, if you would like to borrow this filter to test, let me
                                  > > know. I
                                  > > > > have 2 of them. Or if you would like one, would you take a
                                  > > partial
                                  > > > trade
                                  > > > > for one of your Ha filters <g>? Besides, it's galaxy season so
                                  > > the
                                  > > > wide
                                  > > > > field FS60C is not seeing any light.
                                  > > > >
                                  > > > > Bob
                                  > > > >
                                  > > > >
                                  > > > >
                                  > > > >
                                  > > > >
                                  > > > > -----Original Message-----
                                  > > > > From: Don Goldman [mailto:donclearview@y...]
                                  > > > > Sent: Thursday, April 01, 2004 7:13 PM
                                  > > > > To: ccd-newastro@yahoogroups.com
                                  > > > > Subject: [ccd-newastro] Re: question about strange results from
                                  > > LPR
                                  > > > > filter
                                  > > > >
                                  > > > > > Bob
                                  > > > >
                                  > > > > For some reason this didn't post. I'm resending it now. If it
                                  > > > appears
                                  > > > > twice, sorry about that!
                                  > > > >
                                  > > > > I didn't know about the Schuler "Not V (=violet) and IR filter",
                                  > > > but
                                  > > > > did a little research. I see Anacortes sells it. No curves
                                  > > > > published, but.........I have my ways. It gradually cuts on
                                  > > where
                                  > > > it
                                  > > > > transmits about 50% at 430 nm and then slowly tails down in the
                                  > > NIR
                                  > > > > similar to the Schuler red and luminance filters that I have
                                  > > > plotted
                                  > > > > on my web site. This eliminates the blue halos and fringing in
                                  > > the
                                  > > > > less expensive refractors and would be perfect for the web cams,
                                  > > > > likely better than the Baader filter. Peter was right. 400 nm is
                                  > > > too
                                  > > > > early to cut out fringing in some of the lower cost refractors.
                                  > > > > That's why Lumicon came out with the -violet filter some time
                                  > > > ago.
                                  > > > > For CCD imaging, the blue filter will take a hard hit and you
                                  > > will
                                  > > > > likely have to weight it ~3x compared to green. I think I have
                                  > > > been
                                  > > > > unknowingly biased, since my TAK FSQ is so incredibly corrected
                                  > > > that
                                  > > > > I don't see the problems that people see in less expensive
                                  > > > > refractors. Hope this helps and thanks for getting me to dig
                                  > > > around
                                  > > > > and find out more about this Schuler filter.
                                  > > > >
                                  > > > > Don Goldman
                                  > > > > www.astrodon.com
                                  > > > >
                                  > > > >
                                  > > > >
                                  > > > >
                                  > > > > --- In ccd-newastro@yahoogroups.com, "Bob Holzer" <b.holzer@c...>
                                  > > > > wrote:
                                  > > > > > Don:
                                  > > > > >
                                  > > > > > By any chance have you measured Schuler's Not IR/UV filter?
                                  > > I've
                                  > > > > been
                                  > > > > > using it to cut blue bloat on my Tak FS60C with great results,
                                  > > > but
                                  > > > > just
                                  > > > > > wonder how the numbers actually compare to the Baader.
                                  > > > > >
                                  > > > > > Thanks,
                                  > > > > >
                                  > > > > > Bob
                                  > > > > >
                                  > > > > >
                                  > > > > > -----Original Message-----
                                  > > > > > From: Don Goldman [mailto:donclearview@y...]
                                  > > > > > Sent: Thursday, April 01, 2004 3:11 PM
                                  > > > > > To: ccd-newastro@yahoogroups.com
                                  > > > > > Subject: [ccd-newastro] Re: question about strange results from
                                  > > > LPR
                                  > > > > > filter
                                  > > > > >
                                  > > > > > Peter, just spectrally measured the Baader filter here at
                                  > > work.
                                  > > > > The
                                  > > > > > small peaks that you see posted at Adirondack below 400 nm are
                                  > > > > > there. They amount to only about 4% of a typical blue filter
                                  > > > > > transmission, and about 1.5% of the Red+Green+Blue. Since the
                                  > > > CCD
                                  > > > > > QE drops off so strongly below about 420 nm, these peaks will
                                  > > not
                                  > > > > > have much of an effect. I think this is an excellent low-cost
                                  > > > > filter
                                  > > > > > for the web-cams.
                                  > > > > >
                                  > > > > > Don Goldman
                                  > > > > > www.astrodon.com
                                  > > > > >
                                  > > > > >
                                  > > > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanp@e...>
                                  > > > > wrote:
                                  > > > > > > The curve that I was referring to was the one on the
                                  > > Adirondack
                                  > > > > web
                                  > > > > > > site. There, below the sharp cut-off at 400nm, is another
                                  > > peak
                                  > > > > > > extending down to nearly 300nm. Did the curve that came with
                                  > > > your
                                  > > > > > > filter extend the data down to 300nm? Certainly moving the
                                  > > cut-
                                  > > > > off
                                  > > > > > to
                                  > > > > > > 430nm eats into the blue flux, but unfortunately that seems
                                  > > to
                                  > > > be
                                  > > > > > > where any APOs that I've seen data on start to become
                                  > > > diffraction
                                  > > > > > > limited (hence the blue halos otherwise).
                                  > > > > > >
                                  > > > > > > Peter
                                  > > > > > >
                                  > > > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                                  > > > > > <donclearview@y...>
                                  > > > > > > wrote:
                                  > > > > > > > Peter, the scan that came with the Baadar showed very sharp
                                  > > > > > cutoffs
                                  > > > > > > > at 400 and 700 nm with the UV and NIR blocked.
                                  > > > > > > >
                                  > > > > > > > I find it hard to accept your premise about a filter that
                                  > > > > blocks
                                  > > > > > up
                                  > > > > > > > to 430 nm. That does not leave much in the blue spectral
                                  > > > > region,
                                  > > > > > > > although it will certainly remove blue halos in refractors,
                                  > > > as
                                  > > > > > does
                                  > > > > > > > the minus violet filter from Lumicon.
                                  > > > > > > >
                                  > > > > > > > Don Goldman
                                  > > > > > > > www.astrodon.com
                                  > > > > > > >
                                  > > > > > > >
                                  > > > > > > >
                                  > > > > > > > --- In ccd-newastro@yahoogroups.com, "erdmanpe"
                                  > > > <erdmanp@e...>
                                  > > > > > wrote:
                                  > > > > > > > > The Baader UV/NIR filter does block NIR, and may be the
                                  > > > best
                                  > > > > > filter
                                  > > > > > > > > available for the purpose. But I remain confused how it
                                  > > > can
                                  > > > > be
                                  > > > > > > > called
                                  > > > > > > > > a UV blocker when it has appreciable transmission down to
                                  > > > > nearly
                                  > > > > > > > > 300nm. At that point atmospheric ozone is the more
                                  > > > important
                                  > > > > > > > blocker.
                                  > > > > > > > >
                                  > > > > > > > > I'm still waiting for a properly designed UV/NIR blocker
                                  > > > > > suitable
                                  > > > > > > > for
                                  > > > > > > > > APO refractors, tranmission range of 450-850nm where they
                                  > > > are
                                  > > > > > mostly
                                  > > > > > > > > still diffraction limited. Everything presently cuts off
                                  > > > at
                                  > > > > > 700nm
                                  > > > > > > > > (too early, wasting light) and transmits down to below
                                  > > > 400nm
                                  > > > > > (much
                                  > > > > > > > too
                                  > > > > > > > > far).
                                  > > > > > > > >
                                  > > > > > > > > Peter
                                  > > > > > > > >
                                  > > > > > > > > --- In ccd-newastro@yahoogroups.com, "Don Goldman"
                                  > > > > > > > <donclearview@y...>
                                  > > > > > > > > wrote:
                                  > > > > > > > > > Alex,
                                  > > > > > > > > >
                                  > > > > > > > > > The Meade, and I suspect, Celestron LPS filter let near-
                                  > > > > > infrared
                                  > > > > > > > > > light pass to the web cam. The Meade LPS blocks UV.
                                  > > > Don't
                                  > > > > > have
                                  > > > > > > > any
                                  > > > > > > > > > data on the Celestron. The chromatic aberration you're
                                  > > > > > seeing is
                                  > > > > > > > > > likely related to this. I saw it in my own web cam.
                                  > > The
                                  > > > > > more
                                  > > > > > > > > > expensive Hutech/IDAS LPS blocks UV and NIR but may not
                                  > > > > > provide
                                  > > > > > > > good
                                  > > > > > > > > > overall color balance for your camera. I think the best
                                  > > > > > solution
                                  > > > > > > > is
                                  > > > > > > > > > to buy the new Baadar UV/NIR cutoff filter for $42. It
                                  > > > > > solves
                                  > > > > > > > this
                                  > > > > > > > > > problem. I bought mine from Alpine Astronomical, but I
                                  > > > > think
                                  > > > > > > > > > Adirondack now sells them, too.
                                  > > > > > > > > >
                                  > > > > > > > > > Don Goldman
                                  > > > > > > > > > www.astrodon.com
                                  > > > > > > > > >
                                  > > > > > > > > >
                                  > > > > > > > > > --- In ccd-newastro@yahoogroups.com, "ianderca"
                                  > > > > > <ianderca@y...>
                                  > > > > > > > wrote:
                                  > > > > > > > > > > I have just bought a celestron LPR filter, and I
                                  > > notice
                                  > > > a
                                  > > > > > > > > > remarkable
                                  > > > > > > > > > > cromatic aberration from my photo with webcam but in
                                  > > > > visual
                                  > > > > > > > too:
                                  > > > > > > > > > the
                                  > > > > > > > > > > filter produce a red and blu abberration on the
                                  > > > opposite
                                  > > > > > side
                                  > > > > > > > of a
                                  > > > > > > > > > > star for example, similar but more accentuated than
                                  > > > > > cromatic
                                  > > > > > > > > > > aberration from stars at low level hight. This is
                                  > > > normal?
                                  > > > > > If
                                  > > > > > > > yes ,
                                  > > > > > > > > > > do you mean that you can use this filter only for
                                  > > > visual
                                  > > > > > > > > > observation
                                  > > > > > > > > > > of faint object?
                                  > > > > > > > > > >
                                  > > > > > > > > > > please, if someone have any experience about using it
                                  > > I
                                  > > > > > would
                                  > > > > > > > > > > appreciate any information. I wonder if my filter is
                                  > > > bad.
                                  > > > > > > > > > >
                                  > > > > > > > > > > best regards
                                  > > > > > > > > > > Alex
                                  > > > > >
                                  > > > > >
                                  > > > > >
                                  > > > > >
                                  > > > > >
                                  > > > > > Yahoo! Groups Links
                                  > > > >
                                  > > > >
                                  > > > >
                                  > > > >
                                  > > > >
                                  > > > > Yahoo! Groups Links
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