I used to have such troubles mounting my camera, that I could never get it at 90°. Always was off. So the other night I placed it as accurate as I could and I finally got it at 90°. I knew I had NO desire to move the camera if I couldnt get that back again, so I designed an adapter that I can attach to the camera so if I take it out for transport I can get it back in the same spot. (+/- 1° or so).
Starting to cut out the adapter out of some Delrin I had laying around:
Finished cutting and level installed:
A 4-40 screw (with helicoil installed) pulls the unit together and clamps it into place:
The unit can go on and off in seconds. All I have to do initially is plate solve until I get the camera at the desired angle and then put it on, and rotate it until its level and lock it in with a few turns of the screw and I never have to worry about it again. Seems to be a universal CCD camera size with the body being roughly over 3" in size. Not sure if anyone else had problems, but it was a simple part to design and machine in the course of an evening while I was imaging M13. The delrin is good to probably -40°, and in any case there is zero stress on the part. Really is solid, yet subtle.