I am interested in landscape night photography and would like to avoid star trails. The research I did so far suggests that I should use image stacking to accomplish this but I am having some trouble to find the right program to do this. One thing that makes it a bit more difficult is that I don't want to use Photoshop.
The problem with landscape photography is that is is part sky, which is moving, and part earth, which does not move. So I need a program with quite a lot of manual control so I can make two different stacks, one for the sky and one for everything else. I then plan to edit these two stacks together is Gimp.