A bit stop start tonight as clouds passed over but got a result. It seems I may have been chasing my tail a bit. The mpcc appears to be distorting the star shapes and giving the weird in/out of focus results.
First shots showed FWHM under 4 but stars where out of round. I used ccdinspector to tune collmination but it wasn't till I removed the mpcc that it started to come good.
Here is without mpcc and with mpcc, then the 2 central stars without and with plus a tuc shot for colour. 4x120sec on 253 and about 40x10sec on tuc.
I'm pretty sure my distance to mpcc is within 2mm or less so I'm not sure if the mpcc has issues itself or if the low F ratio is a problem for it. I'll have a look at it's lenses in the daylight tomorrow.
Also the primary cell can move on the lock screws, they are a real pain. This scope originally had a cell with 3 captive screws moving the mirror and if you still have that cell Peter, you'll save yourself some hair if you put it back in
