I've been imaging deep sky objects for about 2 years with an ES ED102. Last month I decided to pull the trigger and upgrade to a C11 Edge HD. With some clear skies and all the accessories needed to get the scope running I was able to set it up and start trying to image at 2800mm... Needless to say it took some time to align the finder scope, check collimation, focus and guide. I was able to take some 5 min subs on M1 and M51 and while guide was great for what I was using with the ed 102, I'm thinking it may need to be better on the C11. My average RMS error was about .4. RA was as low as .19 but the Dec would spike every once in a while causing the ASIair to lose the star briefly. Has anyone experienced this? There are a few things I want to try such as improving the spacing for the OAG to get better focus and replacing the dc adapter for the dew heater (the 15v adapter is too high for the Thousand Oaks controller with the 11" strip). Below is a cropped image of M51 autostretched in PI taken during first light. The dark rings of course are dew which is easy enough to fix, but the star trails are going to be a bit trickier. Does anyone have tips for improving guiding or have the acceptable RMS error for a scope at this focal length?
Right now I'm running the scope into the adapter to the celestron OAG, into a zwo asi120mm-s guide camera without extension tube, then I have the 16.5mm spacer, 11mm spacer and the ZWO asi294mc pro. Does anyone have an example of the spacing for this setup? I know the asi294 requires 55mm of back focus but with an OAG I'm not sure where that should be measured since it isn't a lens like the reducer for refractors.
The mount in use is a CEM60 with 2 21lb counterweights.