[slice of heaven]

Originally Posted by iceman

I've read an article somewhere that suggested that squaring up the focuser isn't 100% necessary to be able to collimate properly.

Here: http://web.telia.com/~u41105032/myths/myths.htm

The keyword in that link is 'accurately'.
What he's saying is a focuser off square by a hair is not dramatic.
I had a page of his bookmarked (I cleaned up my links a while ago and have lost it) where he defines how close to square the focuser should be and the effects this has on the mechanical collimation.
He stated that if it is an 'obvious' error that can be seen by eye, it needs addressing.
The faster the scope the more critical it is.
The link below is for tilt 'across' the tube which is worse than tilt 'along' the tube. But both should be addressed.

http://www.atmsite.org/contrib/Kniff...e/collimat.jpg