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:
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.
>From: "flyrcairplanes" <jeffabbyben@...>
>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