I was experimenting with shutter speeds and ISO settings whilst imaging the Moon with my DSLR the other night and when I got down to a shutter speed of 1/250th of a second starting seeing a problem where the top of the frame had a “ghost” image whereas the bottom of the frame was fine. Here’s a crop of the bottom part of one frame:
And here’s the top of the same frame:
I have frames taken at 1/500th and 1/1000th that don’t show this problem at all.
It’s been suggested to me that it might be caused by the vibration of the mirror moving, so I shall configure APT to pause after moving the mirror and see what happens.