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RE: [ccd-newastro] Star Elongation

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  • Neil Fleming
    I was having similar problems, Jeff. My sample was 4 minute subs, spread over about two hours. Although each individual sub was reasonable, there was
    Message 1 of 12 , Jan 1, 2006
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      I was having similar problems, Jeff.

      My sample was 4 minute subs, spread over about two hours. Although each
      individual sub was reasonable, there was considerable sideways drift over
      the two hours:

      http://autostarsuite.net/photos/hoser/images/4086/original.aspx

      MaxIM reported 0.2 pixel guiding accuracy during that time. I am 99% sure
      that this is differential flexure causing this.

      I was actually imaging through a TV-60IS, and guiding with my NP-127 on a
      TAK NJP mount. Both mounted side-by-side with a Casady Tandem plate.

      ...Neil

      >From: "flyrcairplanes" <jeffabbyben@...>
      >Reply-To: ccd-newastro@yahoogroups.com
      >To: ccd-newastro@yahoogroups.com
      >Subject: [ccd-newastro] Star Elongation
      >Date: Sun, 01 Jan 2006 17:51:06 -0000
      >
      >I am a relatively new to astrophotography and continue to have some
      >star elongation only in the X axis. I image with a TV 102 reduced to
      >f6.9 at 700mm. I guide with Celestron 80mm spotting scope (400mm at
      >f5). I drift align and seem to get good tracking. During imaging I
      >get sub pixel drift. I don't think I'm getting any flexure. Is it
      >possible that the shorter focal length of my guidescope or chromatic
      >abberation is causing my problem? I continue to have problems
      >getting "perfect focus" and don't know if this could be part of the
      >problem. I do have 24 pounds of equipment on my GM-8 and I have a G-
      >11 on the way to help with the large load. Any help would be
      >appreciated.
      >
      >Jeff
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