Collimation Surprise

I modified my ScopeStuff/Antares-style collimator by adding a diagonal target (like the more expensive brands). I also aligned it (thanks, Floyd). Now I can easily see the returned beam while adjusting the collimation of my Discovery 8" F/6 Newtonian.

To my surprise, small adjustments of the wing nuts makes a large, almost random, motion of the returned beam. I'd guess that the friction between the wing nuts and the cell is twisting the mirror position. Has anyone else seen this?

Allen,
Glad my article came in handy, it does make it nice to know your laser is collimated when you try to collimate your scope.
Any tension on the bolts with the wing nuts would result in movement. Just snug them up and check it to see that the beam is still positioned correctly. Practice will make perfect.
Floyd