By performing an extreme stretch of some images resulting from my usual stacking process, I noticed that a "square" pattern often emerges in the background like the one in the below detail cut from a super-stretched stacked image.
To give an idea, given a 32Mpx image, this squares have a size of approximately 350-400 pixels.
Is this an aliasing pattern phenomenon or what else, and how could I fix it?
I shoot with a modded Canon 90D and normal DSLR lenses, always using bias, dark and flat fields to calibrate my light frames before stacking them. I have noticed that these patterns seem not being related to the specific stacking process I use (I've compared the results got with PixInsight and Siril, using different procedures to calibrate and stack images) and observed that the phenomenon is not always evident, but it seems to happen more when I push the zoom to high focal lengths.
Thank you for your support!
