David, I like people fixing their mirror figures, especially when they have concerns about them. I haven't made any claims about my telescopes being "diffraction limited" or even being 1/4 wave (let alone 1/10th or higher.) They could have good figures or not, I really don't know. Criterion marketing materials may have made that 1/10th wave claim in their ads for some of their scopes, but I also think that it's very clear in retrospect that the RV line were not generally 1/10 wave, and I defer to experts, including you, to determine their actual condition.
OTOH, addressing your concern about my particular RV-6 lunar images "Very nice moon shots but again these are low power images...", I'm just showing what they look like, not making any claims that the mirrors are perfect parabolas (or even spheres). Since you seem concerned about "low power" you might be interested in looking at this HIGH MAGNIFICATION VIDEO FROM MY CRITERION RV-8 OF THE MOON THAT I SHOT yon many years ago. https://youtu.be/FUr7CPgS0z8
This is a thumbnail image of that video (i.e. it's not a clickable link image, see link above), which I believe I shot before 2012, but uploaded there in 2012.
Keep in mind if you do watch it that it was shot in 720 in a BestBuy Insignia camera (with no magnification in the camera itself) that I bought on closeout for $20, so watching it on a 4K monitor I'd recommend keeping it in YouTube's default play size to keep it closer to 1:1 (to prevent artificial over-scaling to 4K width to mess up the view.) Please note the crater terracing in the clear 'seeing' moments. You wanted high magnification, here it is. I'm not saying this is diffraction limited, I'm not saying this is 1/10th-1/4th or anything about the mirror figure, I'm just showing how it performs AS-IS. I guess the quality may not be good to some people, but I'm OK with the apparent sub-arc second resolution (in the planet images features obviously smaller than the jovian moon and the Cassini division), even if it might not be getting all the way to the 0.57 arc second theoretical limit of an 8" (and ignoring atmospheric turbulence/diffraction being a wrench in the works of getting there); I'm somewhat disinclined to check the mirror figure(s) soon (but maybe someday when it's re-coated?)
Very nice moon shots but again these are low power images so not at a magnification to be diffraction limited. That is just math behind the imaging so they are not a critical test of optical quality.
Look at the wonderful images Schmidt camera produce but these are low power wide angle views. The optical error only have to be smaller then the grains on film or the pixel size not to be visible. So these optics are not operating at diffraction limits. It is same with many day modern day optics. Binoculars are another typical example. The objectives are usually F/3 achromats so they have about 1/2 wave or worse of chromatic aberration but since they have fixed low power magnification the chromatic aberration isn't magnified enough to become objectionable.
Edited by Jason H., 21 February 2021 - 03:39 PM.