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Re: focusing a 35mm lens attached to ccd

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  • photoshane
    LaMont, I saw your posting about trying to focus your CCD on a 35mm lens. Sounds like your CCD chip and camera lens are not parallel with each other. This
    Message 1 of 5 , Jan 2, 2002
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      LaMont,

      I saw your posting about trying to focus your CCD on a 35mm lens.
      Sounds like your CCD chip and camera lens are not parallel with each
      other. This would be one reason you are getting bloated stars that
      are bigger towards one side, compared to the other. Sky &
      Telescope's current issue, February 2002, has an article on page 117
      by Steve Mandel. His article is all about shooting with SBIG CCD
      cameras and 35mm Nikon lenses. He makes an adaptor to hook up SBIG
      CCD's and the CFW color filter wheel to Nikon lenses. It has a very
      thin profile and allows the use of the filter wheel. It has been
      listed in S&T's new products section some time in the last few
      issues. The adaptor sells for $225-250.

      His article is listed at the S&T web site below
      http://www.skypub.com/skytel/contents/current.html

      If you don't subscribe to S&T, go out and buy this issue off a
      newsstand.

      He uses a RoboFocus with a long rubber belt to drive the focusing
      ring on the Nikon lens in very small and repeatable increments. This
      makes focusing much easier than "guessing" manually, but doesn't meet
      your requirement for "cheap" since the RoboFocus is a few hundred
      dollars too, I think. Unless you already have a RoboFocus...

      Since you are in such a light polluted location, are you using a LPR
      filter from Hutech?

      I saw you live just outside Philly. I live in Nazareth, PA.

      I hope the above info helps.


      Sincerely,
      C. Shane Santi
      C. Shane Santi Photography
      http://www.cshanesanti.com

      --- In ccd-newastro@y..., "LaMont Cranston" <w1828@h...> wrote:
      >
      > I was out tonight trying to do some imaging with a 35mm lens on my
      ccd
      > piggybacked onto the scope. I could have had a few decent images
      but I
      > couldn't quite get into focus. The stars were slightly bloated to
      one side.
      > It was pretty clear it was due to focus because when I defocused
      more, the
      > bloating got worse.
      >
      > I'm looking for a cheap and easy way to focus better than just
      looking at
      > the monitor screen and making my best guess. Would it work to make
      a mask
      > similar to what is used to focus a scope? It would be simple enough
      but I
      > was thinking that the small holes wouldn't let enough light into
      the lens,
      > even if I used a very bright star. Would a mask work or should I
      forget it?
      >
      >
      > LaMont Cranston
      > Cheltenham, Pennsylvania USA
      > 39 53 N, 75 15 W
      >
      > http://w1828.homestead.com/MYPAGE.html
      >
      >
      > _________________________________________________________________
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