Open source alternative for RegiStar (align, rotate, and combine images into single frame) I'm looking for a free, open-source and Linux compatible alternative to the RegiStar software.

I need it to automatically combine several images into a single frame, where each individual image shows a portion of a large observed region.

Individual images also overlap by some amount, and need to be aligned and possibly rotated before superimposing them onto the final frame.

I believe RegiStar does all this but: a- it is not free, b- it is not open-source, and c- it seems to run on Windows only.
I've had success with Hugin. It's a panorama creator, but it can be used to rotate, resize, and relocate images into a coherent whole. It has a few different automated profiles, but sometimes they are a bit off with star stacks. You can manually select the guide stars though.

A really good program for after that is GIMP and the plugin G'MIC to stack and remove noise.

Unfortunately it's not a single package like RegiStar, but it's free and can do quite a lot!

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