celestron c-90 collimation question
Posted 20 October 2005 - 05:25 PM
Does anyone here know how to collimate this old OTA. I find three screws on the back but they don't seem to have an effect. Any help is appreciated.
Posted 20 October 2005 - 06:06 PM
It might be shimmable with a complete dismantling.
What are you seeing that suggests it is out of alignment?
A lot of these never focused the stars to points, but were kind of like inexpensive binoculars, with astigmatism being the predominant focus aberration.
Posted 20 October 2005 - 07:14 PM
What I am checking is the daylight collimating routine. By that test the rings are not concentric around the secondary and shadow. If I can improve it then i will. if it is as you say, I'll live with it. It seems like a good piece of glass, although I really don't have the experience to say that for sure. I just want it for a fast setup when I don't have the time for my xt10 eq. Plus it was free.
Posted 20 October 2005 - 08:27 PM
It's possible to open the scope up without too much difficulty. Good time to relube the helical.
Posted 22 October 2005 - 07:38 PM
It may not be collimation, but a drifted secondary. In any case they need to take it apart to fix, so same problem.