Focusing issues? Ideas?

OK I recently got an Orion XT8. I believe i got it collimated OK (It looked like the picture in the manual ), but some objects would not seem to come all the way into focus. Jupiter looked great, a bit fuzzy, but no more than I would expect. When I tried to split any stars however, they pretty much remained a fuzzy blotch in the eyepiece. The focuser had plenty of travel on both sides of the "optimal" focus, so I dont think anything there was going wrong.

My only ideas are these :
-First off, there were a few clouds in the sky on the horizon, but there didnt appear to be any where I was looking... But I suppose there could have been some haze I was unable to see with my eyes?
-Something out of collimation?
-I don't think any of the optics were dirty, but don't really have a clear idea of what parts might make an image look blurry if they are dirty.
-I'm an idiot, and was just doing something obvious wrong.

You can guess which I'm leaning twords. Any help is appreciated.

Thanks

A couple of observations:

Getting good performance from a Newtonian requires 3 things beside good optics:

1. Collimation. This is pretty important for getting sharp images, not so easy to do. The explanations in the manuals are pretty sketchy and there are lots of holes to be filled..


Sky and Telescope has a page on Collimation and I believe it was written by the master of it all, Nils Olof Carlin.

Also I like this one, "No tools collimation."

http://www.vvm.com/~piscescs/collimat/NoTools2.html

2. The scope must be cooled down. When you take your scope outside, all of a sudden the mirrors start to cool and the mirror distorts. Also the tube cools off and in the process causes convection currents. This all disturbs the image. I takes an hour or so for the scope to cool so that you can get those nice sharp images. Also, if the night is cool, just touching a metal optical tube can cause tube currents, wear gloves if possible.

3. "Seeing", the atmosphere must be stable to get those clean sharp splits. The light from one star passes through a column of air 8 inches in diameter and many miles thick, if that column is not stable, the image will not be stable either. If the stars are near the horizon, this effect will be much worse, normally one should not expect good views when the target is less than 30 degrees above the horizon, or when one is looking over buildings, trees etc.

Hope this helps

jon