Dark Column

[shurik]

This is a strange phenomena: My CCD has a dark column visible in all images at the same place, however when I take series of dark frames, its no longer present and subsequently can not be fixed during calibration/registration process of the light frames....any suggestions why this happens and how to deal with it?

thank you! Alex

[sreilly]

Have you tried applying a bias frame?

-Steve

[shurik]

if 3 minute dark frame does not have a column, how can a 1 second bias frame fix it??

[naavis]

Could you present example light frames and flat frames?