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Originally Posted by matt
I'm getting eveything nicely lined up in the cheshire and the concentric rings look good in star tests outside focus ... but inside focus is a different story - can hardly see any rings and the white area of the unfocused star is dimmer and less defined???
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This is very likely just related to seeing conditions and nothing to worry about.
My mirror star tests very well in great seeing, but on 90% of nights the rings inside focus look mushy and ill defined, whilst outside focus they look ok.
Meaningful star testing for optical quality in larger scopes demands excellent seeing conditions and a well cooled scope.
A few years ago I owned a Saxon 8 inch f5 dob, which I suspect has the same optics as the Skywatcher. Star testing showed obvious spherical abberations but even that being the case, my best ever views of Jupiter were through that scope, even though my present scope has superior optics.
The point being that with larger scopes your limiting factor is likely to be seeing conditions 95% of the time.
If objects look good in focus thats the most important thing
