Are there any free stacking programs for Mac? Starstax is the only one I know and I don't think that it stacks wide angle shots well ie the stars in the corners of wide angle shotsThere are other astro image processing apps out there such as PixInsight, Astro Pixel Processor, and DeepSkyStacker (free) that are excellent for stacking and automatically align the images. It won't help for quickly changing phenomena like an Aurora, but for Milky Way panoramas and other star photos, they can be very powerful. Admittedly, I haven't used them for panoramas that include a (moving) horizon, but I use PixInsight quite a bit for astrophotography. Stacking hundreds of images is easy.