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thanks erick.
Just observing at the moment.
It's a 2" crayford with adaptor and both only have set screws. I've been looking at the GSO and Bintel 2" crayfords and their finish seems a lot better than the SW's. But it does work as a focuser OK - it's just the sloppiness with the cheshire. Maybe your suggestion with the contact padding will work with the set screws.
I can see the whole primary only by looking into the focuser without a peephole and pushing my eye in as far as it can go.
At the moment center field stars do have some coma but it seemed better when I first got the scope and before I tried to 'improve' the collimation (my biggest mistake).
I've never been able to get concentric circles from star testing (using a 4mm EP), only spikey patterns (diffraction?) which I've always put down to the seeing conditions. Jupiter and Saturn don't look too bad in the center. How much of the field should be sharp if the collimation's the best I can get with just a cheshire? 50% too much to ask?
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