Almost any astronomy processing software does this for free, because when you stack a whole load of images it rejects outlier pixels (e.g. a trail present on only one image out of hundreds).
replyIt then usually gives you an image of both the combined success, and an image of just those pixels that were rejected. So, this.
An astronomer would presumably not erase the stars.
replyWhy not? Stars are boring, the cool things are galaxies.
replyActually, this is pretty common for non-scientific astrophotography! Erase Stars -> Edit background and stars colour, contrast etc separately -> Recombine!
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