Thanks all
Im using a 20 year old Meade 6 inch F3.6 Schmidt Newtonian "Cometracker". It has an uncoated plate glass corrector plate (looks dark green from edge on) However I do use the much newer Baader MPCC coma corrector that flattens the field better.
Heres a reprocessed version that is better flatfielded and a bit smoother
Not too bad for an unmodded camera. Im keen to see first pics from a modded 450D owner
Scott