That's correct. For an "added bonus" you could even use one of those magnetic angle finders and skip the ring all together. This assumes that you have something magnetic to stick it on...lots of aluminum on mounts. To do that accurately you would need to:
- Level the scope (this is pretty important)
- Record/zero the angle on the angle finder
- Calculate the offset
- Rotate the camera with attached angle finder + offset.
Probably easier with an example. Say you're at 28 degrees and want to go to 92:
- Level the scope (as in parallel with the ground, since this is reference here on earth)
- Record angle with angle finder using reference surface...lets say it's 14 degrees.
- Calculate offset of sky angle 92-28 = 64
- Rotate camera to offset + current (14 + 64 = 78)
Something like this:
http://www.garrettwade.com/magnetic-bevel-box.html
Thanks,
Jared