Despite taking a full set of bias, twilight sky flats and darks, all my images taken with my ASI017MC camera attached to a Meade 10" LX90 at F10 have a strong colour gradient from top to bottom (lighter at top and very dark at bottom). Whilst I can remove it using Maxim DL gradient removal, does anyone have any idea what could be causing it. PS. the star images across the full image are not distorted.
