If the camera is rotated 180* with a meridian flip in the middle of a filter series, which camera orientation would you use for the flats?
Dave Bailey

Dave,

On my system, I am able to use flats taken from any rotation angle.

If you cannot use the same set of flats for both sides of the meridian, then you would have to take flats for both rotation angles.

In CCDAP we have added the Rotate option in the flats tab. That will allow you to take flats at the post meridian rotation angle and then take another series of flats (with rotate checked) that will rotate the camera 180 degrees and then take more flats. This works with SkyFlats as well as manual flats.

The new version of CCDAP (2.54) places the rotation angle of the file name of the image for easier file management.

rb