AstroPile: Astro Image Stacker

One phone photo of the night sky is mostly noise. Stack a dozen shots of the same scene and the noise averages away while the faint detail stays — that is what astrophotographers call stacking. AstroPile does it on your phone, entirely offline: no network permission, and no photo is ever uploaded. WHAT MAKES IT DIFFERENT IS THAT IT TELLS YOU WHAT HAPPENED. Most stackers hand you one picture. If it came out smeared, you have no idea which frame ruined it. AstroPile gives every frame a report card: • how many stars were detected • how many matched the reference frame • the alignment residual, in pixels • a 0–100 quality score Frames that could not be aligned say why — too few stars, too bright, no matching star pattern, residual too large, different pixel size — plus one line on what to change. Untick it and stack again. HOW IT WORKS 1. Pick two or more shots of the same scene 2. Choose…