The night I watched a satellite tumble through a photo and realized I'd been stacking frames wrong for 2 years

I was at a dark sky spot near Lake Michigan last weekend, trying to get a clean shot of the Andromeda Galaxy. After about 40 minutes of exposures, I saw this weird streak in my preview that looked like a blinking star. Turns out it was a tumbling satellite reflecting sunlight, and it totally wrecked my stacked image because I didn't check each frame before throwing them into the software. I had always just trusted the automatic alignment, but after that night I started manually reviewing every single sub frame before stacking. It took way longer, but my next shot of the Orion Nebula came out way sharper with zero satellite trails. Now I spend an extra hour checking 50 frames to catch the bad ones. Has anyone else had a rogue satellite or plane ruin a perfect night of imaging?

3 comments

3 Comments

spencer_owens581mo ago

That tumbling satellite in your Andromeda stack is rough but honestly you got lucky catching it after only 40 minutes. I had a similar issue with the California Nebula where I stacked about 120 frames and only found out later that a plane flew through the corner of like 15 of them. Did you find your auto alignment software was still trying to use those bad frames to match stars, or did it just reject them automatically once you pulled them from the sequence?

wesleyb201mo ago

Actually I'd argue the complete opposite - you should keep those flawed frames in the stack and let the software handle it. I've been doing this long enough to see that a lot of these auto rejection tools get too aggressive and end up tossing frames that could actually contribute useful data. I had a Moon shot last year where I let the alignment software auto-reject frames with a plane trail and it dropped half my stack because it flagged every slightly uneven exposure as bad. Ended up redoing the whole thing manually keeping everything in and the final image came out way better. Your California Nebula frames with the plane in the corner - the stacking algorithm usually does a fine job just averaging over the trail as long as you have enough clean frames. Why throw away perfectly good signal from the rest of that frame just because something drifted through a corner?

lewis.finley1mo ago

Yeah, mine just tossed them out once I removed them from the file list before stacking.