... differential flexure?

[lukebl]

SteveP, your message promted me to have a closer look at the separate images.

The attached image is a closeup of part of the frame, with all six frames stacked but not aligned. The stars are moving from left to right, and the gaps between the start of each frame is 7, 6, 10, 11, and 7 minutes. The exposures on each were 158, 180, 276, 237, 182 and 183 seconds. (obviously the time between the end of one image and the start of the next will be, for instance, 7 minutes minus 158 seconds)

The stars are somewhat elongated, but the odd thing is that the axis of their elongation doesn't seem quite the same as the direction of drift. And, as you say, the elongation doesn't seem to be as much as the drift between exposures. Or maybe I'm seeing things.

Confused. Unfortunately, it looks like it will be cloudy here in Norfolk for the next few nights so I can't persevere with this one! Any further clues would be most welcome.

Cheers,

Luke

[lukebl]

... and here's the completed stacked image.

Thanks,

Luke