Here's 3 test shots I did in Ha Tuesday night. M8 (15min) , the Helix (20min) and the Tarantula (20min). All in 30s exposures. Calibrated and flat fielded. Lost focus as time went past. Next run I'll have to check regularly when slewing to different targets.
The C11 was fitted with my new toy, an Hyperstar 3 that reduces the C11 to F/1.8, that's 504mm FL for 11" aperture. The Lens is fitted directly on the corrector plate by removing the secondary. So the camera hangs off the scope front. There are pictures of the
system here. I haven't collimated the system yet and all the shots were 30s unguided.
Not pretty pictures by any mean but what's interesting is the total exposure time on each object. A 30s exposure with this system is roughly equivalent to a 10-15min sub with my 5" newtonian.
You can actually see the core of the tarantula starting to burn already at 30s. When I have the whole rig collimated properly and I figure out how to guide it I'll be able to go deeper and minimise the noise.
If you are currently using an SCT, even as small as a C8 it's worth looking into those lenses. It will save you a lot of exposure time which is an added benefit with the weather lately. You can get a lot more done in less time.