sv550 122 ff spacing

0.8x ff

 Here we are with no filter, so with the 533 sensor at 17.5mm, from the m63 to m48 adapter telescope side we have:

extension tubes:    20+10=30

m48 to m42 adapter:       06

atr533 backfocus:         17.5

TOTAL:                    53.5mm

It seems OK and TBH, I'm fed up trying to get the thing set optimally. Too far -> bloated stars. Add a filter -> bloated stars. But that was at 57.5mm. So, despite the wind and drifting cloud, let it autofocus and something decent emerged for a change without having to jump through hoops processing. 

gemini focus 5356

open clusters m35 with ngc2158 in gemini
atr533c on sv122    21x3min @ hcg100