I've spent the last couple of years using an ES80 fl600 and have just changed over to the C11 with fl2800 (possibly adding a 0.63x focal reducer).
I got errors in pointing of between 1 and 4 minutes.
I've got both the gsc and USNO A2.0 Catalogues and have the USNO A2 selected.
What are the main points to take into account when switching to a higher focal length?
Obviously the ed80 was easy as it was at worst a 4 arcmin error in a 30arc min field of view.
I do seem to have an error in the C11 optical path as one of the few successfull results i've had displayed an fl of 3174 but the ra and dec spot on, i suspect i rotated the corrector plate when assembling the c11 so that it's now not matching the mirror.

As ever any comments welcome otherwise i'll just keep plodding along and playing.
set up the focusing last night and it's working well.
Finally managed a guider calibration after hundreds of guide star not found messages from maxim dl, which is very frustrating when you can see 6 really perfect ones on the sensor and it ignores them.
The C11 looks great on the mesu I'm looking forward to doing a horses head this winter if i get a clear night.

Sent from my SM-N9005 using Tapatalk