[Rob_K]

Amazing what you can see when you look a little deeper into your shots!

The "5 Asteroids & 2 planets" shot I posted earlier shows a faint trail of dots in the bottom right corner. I just cursorily dismissed it as a hot pixel trace (no tracking), but then it occurred to me that I had re-positioned the camera on the tripod 3 times during the sequence. A search of the original stack of 20 15-sec exposures revealed a hot pixel trace that did jump each time the camera was re-positioned (heavily stretched crop attached for reference).

So the 'object' appears to be real. The total elapsed time for the sequence was 9 min 30 sec, and the apparent movement against the starfield was 2.4 degrees, measured approx with the measuring tool in Starry Night Pro 5. This would indicate a period of about 24 hours - ie staying in the same spot relative to Earth while the starfield rotates (not quite true as apparently they do a slow figure-8 relative to the observer, unless geostationary). An actual size crop from the stack, labelled, is attached. On each frame, the object is considerably brighter, probably mag 7-8. Stacking has dimmed it, particularly to the left.

This would suggest a geosynchronous satellite, but I'd be interested to hear any comments from keen or knowledgeable satellite observers/imagers out there. Thanks.

Shot details: Canon 400D on tripod; crop from 20 frames stacked in Deep Sky Stacker, each 15 sec at 18mm, F/3.5, ISO 1600. Stretched in PS CS2 & saturation of asteroids included was selectively increased to 100%.