Here's a 3.5 hour result on NGC55 from my backyard in Perth. I actually managed to get some good seeing, and it was good to be able to iron a few bugs out of the system. The scope is a 10"f4.5 with a qsi683 camera on a G11, with a 0.953" image scale.
Still some issues with what I think may be stray light causing the ring, but I have an alternative theory that it is fact caused by taking the flats with the focuser in the wrong position.
Full res on astrobin:
http://www.astrobin.com/133436/
cheers,
And thanks for looking!
Andrew.