"
The main mirror is shifting within the OT"
You have affirmed what legions of SCT imagers have known for decades. ?I'm surprised that you were unaware of this, as it is often discussed in many forums.?
There are marginal cures, such a "Flop Stoppers". But piggy-back is inherently problematic - the primary is not the only component subject to flexure and solving it may not actually solve the real problem. ?
OAG is the standard "best" solution but can be a real pain. ?A high quality and precisely aligned mount goes a very long way. ?
And the low read-noise of newer cameras permit shorter exps that can eliminate the need for any type of guiding (other than keeping the target within the frame). ?CMOS is still problematic for most DS but the very low noise promises sub-exps as short as 5-20 sec that do not benefit from guiding. ?
This is an extreme example, but here is a recent image made with my new Egde C11 using EMCCD at 8fps (0.125 sec x 55k frames) with no guiding:
Stan
