Took it out briefly for the first time tonight, only briefly due to one of the tripod legs sinking slightly making actual polar alignment night impossible! Didn't have the energy to dismantle the system, move and revelled the tripod and then setup again.
Mistake learned from, use concrete and not grass
Grass position has a better view of sky, concrete has less tripod sinkage however.
Anyway, I have a strong feeling that I must have the spacing wrong with my flattener reducer, getting ~40% curvature! From the attached mosaic it is VERY evident. I guess my theoretical 0.5mm off is far more than that!
When I've got time (hopefully in a week or so) I am going to knuckle down and write a review of the scope. Preliminary playing with says it is a very solid well constructed scope
Now I've just got to figure out how to get the most out of the damn thing!
I am actually quite curious as to how much of the vignetting has been caused by the heavy curvature. This is actually one of the reasons for the initial post on vignetting, it seemed higher than I was expecting and maybe this is a contributing factor.