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Posted by Bob Sal on February 28, 2002 20:11:19 UTC

I'm no expert on collimating an SCT, but it does sound like yours is out. I've seen a few that needed collimating. When focused, as best it could, the stars looked like small comets. They never focused to points. When out of fucus the circle was off center and had a dim fan shape next to it. We had a very good lecture on Collimating at a club meeting once. We had a speaker who knew his collimation. Much of the stuff I've described looked like the examples he gave. Don't know if your pie with a piece missing is one of them. Is it kind of a fan shape? Anyway, the guy said not to be afraid to touch the collimation screws. Just don't turn them too much. 2 to 3 full turns and the secondary mirror can fall off into the tube. 1/4 turn should be a very dramatic difference.
Also, I know a guy with the 9.25 Celestron. He said the same thing, the mount is very shaky. The scope is undermounted. Higher magnification will only make it worse. Don't know how you can fix that except get a bigger mount. That's how they keep the price down. They sell you the big scope on too small a mount.
That's it;
BOB SAL

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