OK follow up.
Thought I'd try tightening up the Bob's Knobs to see if that has a positive effect.
I don't want to jinx myself but I think I see an improvement
I've tightened them up pretty tight but being a comparative newbie to SCTs I've got no idea of what is too tight or too loose.
The stage they are at now is finger tight. I don't think they're too tight. They could be tightend further but right now they're pretty firm. Obviously I don't want to tighten them to the point where it puts stress on the seconday or the corrector.
So I'd like to ask some of you more experienced SCT folk: what's the visual sign/s that you've tightened the collimation screws too tight????
How does it effect the image???
Your help much appreciated.