Mr stop up late (h0ughy) decreed that it was "too late" (or too early) in the morning and that M42 would be washed out in the early morning glow (just before 4AM). Being a stubborn southerner I decided to give it a bash anyway. The core is burned out but I'm happy enough for a single shot.
Thanks guys for the comments, re the nice round stars, the standard Skywatcher flattener is a pretty good item with the ED80, on the full frame at the very edge corners there was some slight eggyness if wiewed at 100% res, but I suspect that was a function of less than optimal focus as not all shots exhibited that trait. Hopefully I'll get some more data to add to the 3 subs I have and can tease out sone detail in the core.
