Tried stacking my 11th photo of M31 and the noise got worse instead of better

I added 30 minutes more exposure thinking it'd clean up the background, but my stack actually ended up with weird streaky artifacts. Anyone know what causes that with deep sky images?

2 comments

2 Comments

holly_walker761d ago

Honestly been there and it's so frustrating. Usually those streaky artifacts happen when you've got walking noise or when the dithering between frames wasn't aggressive enough. Ngl I had the same thing happen stacking M31 a few months back and it turned out my guiding was drifting just a tiny bit every frame. Might be worth checking if your subs have any trailing or if the dither steps are set high enough to really shake things up between each shot.

allen.charlie1d ago

I had the exact same thing with M31 back in November @holly_walker76, and yeah, the dithering was the culprit. I was using 120 second subs and my dither steps were only set to like 5 pixels, which just wasn't enough to break up the walking noise pattern. Upped them to 15 pixels and the streaky artifacts basically vanished overnight. The guiding drift is a sneaky one too - I had a polar alignment that was just barely off and it showed up as faint streaks that stacked into a real mess. Had to redo my entire polar alignment and bump the aggressiveness on the dithering to clean things up.