Check the orientation of the camera, before you take a drift scan image
If the camera is in the right orientation, a star moves, at shut of telescope drive, form the bottom(east) to the top(west) of the image (from one standard image to the next).
To adjust the orientation exact, take a standard image with the trails of the stars (Turn off the clock drive of the telescope).Use an exposure time, a little shorter than the time a star needs to move from the bottom to the top of the image, so the ends of the trails are visible.(about 60 sec) A trail of a star should be exact at one column. (You can use a program like CCDOPS and check that using the X-Hairs). If necessary rotate the camera carefully.
As the orientation of the camera should be more exact than 0.1 deg (ST-7) or 0.05 (ST-8), it will be necessary to build an attachment for the camera, which enables you to rotate the camera exactly.