I collimate my 10 inch Celestron SCT all the time according to the instructions that came with it. But I cannot give you direct advice as to how to do yours. The controls may be different. My scope is 30 years old and is no longer serviced by Celestron--they don't even have the blueprints for it any longer! If you don't have instructions, contact the factory of the telescope's maker. They can get you the proper instructions. In any case, it will take VERY LITTLE adjustment. Turning the screws a fraction of a turn to two turns at most is an EXTREME amount of adjustment for an SCT. This is because the relationship between the main and the secondary mirror is so critical. At high power, a decentering of the main mirror's reflec- tion on the secondary really throws the image off to one side at the focal plane. Angles of view at the focal plane are measured in fractions of a degree, so you can see that tilting any component of the optical system is a serious step.