I know this is a GS thread, but I have to concur with Starkler.
My Skywatcher 8" shows the same inside focus fuzziness on a star test compared to the outside focus, which is always very impressive.
The scope is collimated and I get very nice visual images with it, but there is definitely a difference. At least the fuzzy inside image is nice and bright and the inner and outer circle are very circular and concentric. I can still see the airy disc at the centre.
I have noticed the fuzziness varies with the seeing, and on some evenings the number of rings visible is better than others. So it must be as Starker suggests attributable to atmospheric conditions.
