I have been trying to understand the MCT design for a long time and why I like mine so much. I always attribute the great views to the above average seeing and thermal cooling in the tropics. Both of which allow a very high level of collimation. All of this matters.
A question for MCT is (and SCT, too, it's related), how can you take a highly curved meniscus that, apparently, puts out a lot of secondary spherical aberration and toss in a fast primary mirror with a ton of primary spherical aberration and make it work at all. Not only work in many cases, but work quite well. Certainly a scope with that much aberration is not on the same par with a premium scope (except maybe an unobstructed APO). I still believe we can characterize mass production as something of a hit and miss proposition, not saying otherwise. But can we say some premium scopes are being delivered at or above the bell curve? And if so, do those lucky enough to have one, can it be said we have premium optics?
Even though it's massed produced, is it also what we might consider premium? I do not mean premium in the way amateur glass pushers craft well made premium mirrors and professionals deliver sensibly perfect optics to a very satisfied market, and thank God for them, but the way machines might do it. We will often hear that mass produced scopes will be no better than 1/4 LSA, plus a few more aberrations, especially as the system is tested at the eyepiece. So, the popular implication seems to be they simply cannot be premium. Impossible. I might argue otherwise.
An IF certainly takes no prisoners and may well tell us our scopes have 1/4 pvw LSA and a host of other aberrations at a few points sampled, but I can say the (my) star test is most certainly not indicative of a smooth fully 1/4 wave of undercorrection across the defocused pattern as they are argued to be...that they must be, for some reason. Apparently because it cheaper to leave them at 14 pvw LSA. Roddier is probably good test, and DPAC is arguably a good test, as well. But, what if all of these tests show us nice results? Is our scope premium in the level of its performance regardless of whether it's finely handcrafted?
Like many others, I know I have simply been impressed with the MCT design, as others have with their SCT. I have seen some amazing things and discussed observations with other premium owners. Premium owners seem to have a some level of advantage over what I have seen, mostly in terms of "sharpness" (I think I know what that means.) However, that difference may well have boiled down to the size of our obstructions (or lack of), and to some extent the mechanical execution such as baffling, coatings, focuser movement, or glass quality. I am not so sure it's always the premium optics that are making the difference in all cases. So, it dawned on me, if not, then do I have a premium scope. And do you?
The question remains, well, even if it is premium how do you know it is? And at what level of performance can we say it is premium? Maybe it boils down to some scale of Strehl ratios, but it also may not be that simple. Or are premium optics simply hand made and tested (sometimes with a certificate or simply a reputation) to show they are?
Edited by Asbytec, 19 May 2018 - 05:34 AM.