Legion50

That makes sense. Thanks for the explainer

Wow thanks for all the help. Sorry for the late response. I got a lot of ideas from this thread. I think I will try stacking the stacked images first. Maybe test it out by splitting my current set into two and comparing the single stack vs batch stacked images for any quality difference. I haven't had another clear sky yet to test this out though. I will try the 16 bit as well. I may be wrong here, but would using a tracker and reducing the iso actually change the overall exposure? the total integration time increases, but wouldn't the exposure remain similar? I am going from landscape photography to astro, so I keep thinking in terms of the exposure triangle haha.

Im doing a personal project to take a very good picture of the Andromeda. Im in a location with a lot of light pollution (and no transportation to go elsewhere with short notice) and very wet weather generally. I have to take 2 second exposure images since I don't have a tracker (and any longer the photo gets overexposed due to light pollution). I took a total of 26 minutes of exposure the other day and I was very happy with the results (although there is still a lot of noise). I edited the image in Siril. Im thinking of getting more images whenever I get clear skies and to refine the images further. So my main question is on how to stack multiple day images. I can do the preprocessing from each session and get the pp_ sequence together. but each photo seems to create a 280MB file in the pre processing step (and another 280 MB file in the registering step) which adds up very fast. Even the 790 images from the last session used above 400 Gbs of SSD storage which is my limit. So I am wondering if it is possible to optimize this process in any way. Like can I stack each session separately and then stack the stacked images?