Posted 26 June 2012 - 09:31 AM
One would be tiltable in the fore-aft direction, which would cause the image to move up-down. The other would rotate about the optical axis (as coming from the objective, not that as reflected), which would cause the image to move L-R. As long as reasonable care has been exercised in the dimensioning of components and their placement, the rotation of the one mirror in order to effect collimation will be so slight that image rotation will not be an issue.
When I first assembled the 5" f/5, I had adjusted the tiltable mirrors on the rear assembly merely by eye. When I attached this unit to the body, the bino was not far from collimation, only small adjustments being required. I say this to assure you that as long as you observe (my version) of the carpenter's dictum which states, "measure thrice, cut once", your bino will come together nicely and perform splendidly.