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.
Date: November 2008