|
Peter,
Verifying the squareness of the focuser to the OTA in Newtonians can be problematic.
The general method is to place a straight edge across the end of the focuser parallel to the optical axis and measure the gap between the straight edge and the tube at the extremes....
Any differences can be corrected by adding shims between the focuser body and the OTA.
(It's much easier with refractors!!)
Hope this helps.
|