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RE: [ccd-newastro] Re: question about strange results from LPR filter

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  • 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 1 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 2 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 3 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 4 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 5 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 6 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 7 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 8 of 18 , Apr 2, 2004
                  • 0 Attachment
                    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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                    > Yahoo! Groups Links





                    Yahoo! Groups Links
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