Loading ...
Sorry, an error occurred while loading the content.

Re: New Image - IC434

Expand Messages
  • Dean Jacobsen
    Awesome Randy, are you using the 10nm Schuler filter? Dean Jacobsen www.astrophoto.net ... next ... the
    Message 1 of 13 , Dec 1, 2004
    • 0 Attachment
      Awesome Randy, are you using the 10nm Schuler filter?

      Dean Jacobsen
      www.astrophoto.net

      --- In ccd-newastro@yahoogroups.com, "RMarsden" <jmarsden@s...>
      wrote:
      >
      > After the good results on the California Nebula, I was out the
      next
      > night to try imaging IC434 in h-alpha from San Diego. Once again
      the
      > transparency was very - magnitude 3.5 or 4 even when the moon was
      > up. This result is much better than the one I posted after imaging
      > at a dark sky site with poor transparency and fighting dew.
      >
      > The new image is at
      >
      > http://aisig.sdaa.org/astroblogDetail.asp?imgID=315&UserID=55
      >
      > All comments are welcome.
      >
      > Randy Marsden
    • RMarsden
      Dean, Thanks!Y es, I used the 10nm Schuler. Now I am thinking about getting some other narrowband filters. SII and OIII look like good candidates. Now I ll
      Message 2 of 13 , Dec 1, 2004
      • 0 Attachment
        Dean,

        Thanks!Y

        es, I used the 10nm Schuler. Now I am thinking about getting some
        other narrowband filters. SII and OIII look like good candidates.
        Now I'll need to buy another filter wheel.

        Randy Marsden

        --- In ccd-newastro@yahoogroups.com, "Dean Jacobsen"
        <deanjacobsen@e...> wrote:
        >
        > Awesome Randy, are you using the 10nm Schuler filter?
        >
        > Dean Jacobsen
        > www.astrophoto.net
        >
        > --- In ccd-newastro@yahoogroups.com, "RMarsden" <jmarsden@s...>
        > wrote:
        > >
        > > After the good results on the California Nebula, I was out the
        > next
        > > night to try imaging IC434 in h-alpha from San Diego. Once again
        > the
        > > transparency was very - magnitude 3.5 or 4 even when the moon
        was
        > > up. This result is much better than the one I posted after
        imaging
        > > at a dark sky site with poor transparency and fighting dew.
        > >
        > > The new image is at
        > >
        > > http://aisig.sdaa.org/astroblogDetail.asp?imgID=315&UserID=55
        > >
        > > All comments are welcome.
        > >
        > > Randy Marsden
      • Randy Nulman
        Randy, Really nicely done! Congrats, Randy Nulman http://www.nulman.darkhorizons.org ... next ... the
        Message 3 of 13 , Dec 2, 2004
        • 0 Attachment
          Randy,

          Really nicely done!

          Congrats,
          Randy Nulman
          http://www.nulman.darkhorizons.org


          --- In ccd-newastro@yahoogroups.com, "RMarsden" <jmarsden@s...>
          wrote:
          >
          > After the good results on the California Nebula, I was out the
          next
          > night to try imaging IC434 in h-alpha from San Diego. Once again
          the
          > transparency was very - magnitude 3.5 or 4 even when the moon was
          > up. This result is much better than the one I posted after imaging
          > at a dark sky site with poor transparency and fighting dew.
          >
          > The new image is at
          >
          > http://aisig.sdaa.org/astroblogDetail.asp?imgID=315&UserID=55
          >
          > All comments are welcome.
          >
          > Randy Marsden
        • erdmanpe
          Your explanation is quite correct for narrower filters. At f/5 or so you need to start worrying with a filter of about 4nm bandwidth. However, RGB filters
          Message 4 of 13 , Dec 2, 2004
          • 0 Attachment
            Your explanation is quite correct for narrower filters. At f/5 or so
            you need to start worrying with a filter of about 4nm bandwidth.
            However, RGB filters have a bandwidth (depending on the particular
            one) of about 10x that, so it doesn't matter for them. At Ha, with an
            f/2.8 system, the bandpass will shift about 2nm to shorter wavelength
            from that at normal incidence, so a 50nm wide "red" filter would be
            little affected. The wavelength shift is less at shorter wavelengths.

            Peter

            --- In ccd-newastro@yahoogroups.com, "RMarsden" <jmarsden@s...> wrote:
            >
            > Peter,
            >
            > It seems that interference filters should be sensitive to the f-
            > ratio of the optical system. Interference filters are designed for
            > plane-wave incidence where the interfernce effects are uniform
            > across the filter. It would seem that at smaller f-ratios, a
            > significant fraction of the light is not hitting the filter at a
            > perpendicular angle - the light cone is much broader at f2.8 than at
            > f-10. The light coming in off-axis will not experience the same
            > interference as the on-axis light. Depending on the design of the
            > filter, this could cause broadening of the filter bandwidth or
            > create pass or rejection bands that don't exist for higher f-ratios.
            >
            > Does anyone know if the filters we commonly use have a lower limit
            > for the recommended f-ratio?
            >
            > It may be that some camera lenses would not be affected because the
            > final elements often form a field flattener/relay lens assembly that
            > would cause the light to be nearly a plane wave at the filter. But
            > other simpler leneses wouold behave more like a classic refractor.
            >
            > Randy Marsden
            >
            > --- In ccd-newastro@yahoogroups.com, "erdmanpe" <erdmanpe@y...>
            > wrote:
            > >
            > > The f/# doesn't affect the bandpass for such broad filters, nor the
            > > index of refraction (ever). However, a low f/# does make the
            > position
            > > of best focus more sensitive, which is to say out of focus is more
            > > noticable.
            > >
            > > Very nice image, in any case.
            > >
            > > Peter
            > >
            > > --- In ccd-newastro@yahoogroups.com, "RMarsden" <jmarsden@s...>
            > wrote:
            > > >
            > > > Richard,
            > > >
            > > > Thanks. But I also want to do colr. The RGB filters are not
            > parfocal
            > > > with this lens, at least not when wide open. I wonder if the
            > steeper
            > > > angle of incidence at f2.8 is affecting the filter bandpass and
            > > > effective index of refraction. I can get decent focus at f4.5
            > but
            > > > the three filters are not parfocal. I have to focus separately
            > for
            > > > each one.
            > > >
            > > > Randy Marsden
            > > >
            > > > --- In ccd-newastro@yahoogroups.com, "Richard Bennion"
            > > > <rbennion@b...> wrote:
            > > > > Randy,
            > > > >
            > > > > That imaging setup is just working perfect for you!
            > > > >
            > > > > Super image.
            > > > >
            > > > > rb
            > > > >
            > > > > Richard A. Bennion
            > > > > http://www.ewellobservatory.com
            > > > > http://www.ccdware.com
            > > > >
            > > > > -----Original Message-----
            > > > > From: RMarsden [mailto:jmarsden@s...]
            > > > > Sent: Wednesday, December 01, 2004 1:58 PM
            > > > > To: ccd-newastro@yahoogroups.com
            > > > > Subject: [ccd-newastro] New Image - IC434
            > > > >
            > > > >
            > > > >
            > > > > After the good results on the California Nebula, I was out the
            > > > next
            > > > > night to try imaging IC434 in h-alpha from San Diego. Once
            > again
            > > > the
            > > > > transparency was very - magnitude 3.5 or 4 even when the moon
            > was
            > > > > up. This result is much better than the one I posted after
            > imaging
            > > > > at a dark sky site with poor transparency and fighting dew.
            > > > >
            > > > > The new image is at
            > > > >
            > > > > http://aisig.sdaa.org/astroblogDetail.asp?imgID=315&UserID=55
            > > > >
            > > > > All comments are welcome.
            > > > >
            > > > > Randy Marsden
            > > > >
            > > > >
            > > > >
            > > > >
            > > > >
            > > > >
            > > > >
            > > > >
            > > > > Yahoo! Groups Links
          Your message has been successfully submitted and would be delivered to recipients shortly.