I have a 16" f/4.5 dob that is based upon a classic design (i.e. not a lightweight). There is a bit of collimation shift. I have tightened everything (i.e., spider, secondary holder, focuser, truss tube connection points, and the focuser brake/lock), and I have checked the sling to see that it makes proper contact with the mirror. But there is a bit of collimation shift.
I collimate with the scope at 45 degrees. When i move it upward there is a bit of shift. When I move the telescope down there is a bit of shift. So, my question is simple. Is a bit of shift to be expected in a larger telescope? And is there a point where one should learn to live with the shift?
I have not tested the telescope to see if there is a degraded image due to the shift. And yes I know I really should do that.