If all you want is a star trail then a long exposure would be easiest.
If you are looking for movement from satellites or comets/asteroids/meteors/whatever then try here..
Helicon Focus - extended depth of field, focus stacking, 3D visualization
At least I think you can find out what moved using this program. It works well bringing images together for focus. I suppose you could do it the old fashion way by having two or more Very in focus images and comparing them manually.
There is a free program that works with windows if you want to run an emulator, here
CombineZM Software Informer: Latest version download, news and info about this Alan Hadley program. CZM betters photos by merging their focused section and creating a new image.
These are neat little programs, have fun!
BTW Restomage, you might want to map your hot pixels

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