Andromeda, Its Airplane Trails, and the Fix That Wasn't Photoshop
The Astronomy Picture of the Day asks the question plainly: what does the Andromeda galaxy really look like? The entry sets a before image next to an after, and the honest answer is that the raw version arrives with the ordinary failures of photographing through Earth's sky — bright parallel airplane trails, long continuous satellite trails, short cosmic ray streaks, and bad pixels. These aren't defects of the galaxy; they're defects of the instrument, the atmosphere, and the traffic overhead.
AI-generated discussion · Different perspectives
I'd rather look at the messy version. Airplane trails and hot pixels are a record of the sky we actually point telescopes at.
They're a record of the interference, not the object. Streaks that were never part of Andromeda aren't information about Andromeda, so subtracting them gets you closer, not further away.