I was trying out the EOS 600D in 1920x1080 movie crop mode last night, coupled with a 5x Powermate and 12" Sky Watcher Goto Dobsonian. Seeing was below average and transparency very porr due a layer of cloud. Nonetheless I managed a few images at 1/30th sec ISO 1600, all very heavily processed because of the conditions, so hopefully not too offensive
Thanks for looking,
Tom