Hi, all - a quick scope comparison conundrum that some of you might be able to provide some insight on.
I am primarily a deep sky and planetary visual observer - average major city light polution. My go-to scope is usually my trusty old Celestron/Vixen 6" f/5 with excellent optics. I also occasionally use a second hand 8" Meade SCT - an older LX5 of about the same late-1980's vintage. I know the Meades from the '80's are a mixed bag, and this is a pretty average one, with sloppy focus and some degradation of the coatings on the corrector plate.
Rarely do I have both scopes out together, but have the past few nights because of some exceptionally clear and darker skies we've had. I'm using a like-new Celestron f/6.3 reducer and quality 2" diagonal on the SCT, and a superb set of classic Celestron Ultimas to achieve nearly identical magnification and FOV in both instruments. I've been a bit baffled that in a side-by-side comparison, M42 and a number of open clusters actually appear a bit brighter, sharper, more detailed, and far more contrasty in the 6" Newt than the 8" SCT. If anything, images are about the same brightness, but not better in the SCT.
Is it even possible for a 6" Newt to outperform an 8" SCT? Though the 8" has the special silvered optics group, the primary and secondary don't appear to be tarnished or degraded. Could this be simply being caused added surfaces/reflections of the corrector, reducer, and diagonal? Or, it it likely that this scope is past its prime, and the corrector coatings and mirrors are a bit too far gone after 30 years?
Thanks for any thoughts/insights you may have.