M41 with racetrack artifacts

M41 with racetrack artifacts: This is an example of "residual bulk imaging", and the detrimental effect it can have on an image. This is a stack of many subframes as the image "drifted" towards the left. Then a series of short darks were taken that, when subtracted, resulted in the ghost streaks. "Flashing" the CCD before each subframe would have eliminated this effect.

Messier: 41

Date: November 2008

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