Thanks, I suspected similar.... as far as I can tell the MPCC is spaced correctly. I cleaned both mirrors on the weekend and reinstalled/collimated on the bench and then touched up after mounted (not much variation). Of course then the imaging train goes on with whatever tilt is carries?
I took some 1s exposures in a busy star field to try and assess the optical train hopefully ignoring most guiding effects. Guiding last night was pretty 'interesting' though.
This image is a single 1s sub, stretched
very hard to see the stars of course. I've added the corners and centre if it helps.
Link to FITS
Thanks for any advice/analysis.... to be honest I've seen worse from this scope, but I've also seen better, and I refuse to believe I can't have round stars across the small 428EX chip.