Wonderful image Mike. Got to be happy with that. I like the tiny stars. I think apart from getting deep fast that will be a very nice aspect of these AG12 images. These fast Newts seem to get smaller stars than APOs. Lots of detail in the faint background nebula. This would be a great scope to pick up integrated flux nebulas.
Offaxis guiding is totally the way to go. You have more prospect of flex with this setup than your AP with its rigid tube and solid focuser. I tried to use a guide scope on the CDK17 and no way Jose. I just did a run of imaging using a MMOAG on the TEC180 and got rid of the guide scope. What a difference. Fabulous. Plus my setup requires one less counterweight. I saved on the weight of the guide scope, rings. Plus a guide scope makes the setup top heavy which affects balance differently at different angles. The scope is now easier to balance. The MMOAG setup I use is about 55mm thick all told with the adapters.
http://www.pbase.com/gregbradley/image/134562827/large
As far as elongated stars in the corners (not noticeable in the image really unless you super look for it) I imagine that is either a spacing issue or the corrector is not correcting all the way to the edges. I have an FS152 4 inch reducer and it starts to affect corner stars even with the ML8300 chip which is smaller than a DSLR. I could be wrong but I don't think collimation causes elongated stars at the corners. What's your experience with this? I have seen incorrect spacing cause this. I have an AP155TCC corrector/reducer for the AP140. I had it slightly off on one setup (its very sensitive to correct spacing +/- 1mm) and it caused elongated corner stars.
Greg.