[Wavytone]

Dunk, with 45 years experience and roughly a dozen scopes over the years, I'd have readily agreed with you - prior to acquiring the MK91.

For most observers their experience is based on the one scope they have, and they think it's fine simply because (a) the star images look like they should according to most sources, and (b) it performs ok compared to other similar scopes. Many many observers are in this category. All fine and dandy, until the day when someone sets up another scope side-by-side with yours, same targets, same conditions, same magnification (same eyepiece even) and you realise what you are seeing is chalk, vs their cheese. Another clue is that whole most cheers consider magnifications around X1.5 per mm to be the practical upper limit for reflectors or X2 for refractors, to reach Dawes limit on double stars requires X3 per mm of aperture and a few scopes can exceed that on the moon and bright planets.

Yet as anyone with an f/10 SCT would know, an eyepiece under 8mm is pointless, never mind 3.5mm.

Several years ago poking around on the intertubes I stumbled on images taken by owners of MK91s and was struck by the the resolution they were routinely achieving with quite ordinary cameras. I'll skip the details as to how I eventually acquired this one.

Soon after acquiring the MK91 I very quickly noticed at club observing nights this scope routinely gave constantly good high power viewing while 8"-11" SCTs a few metres away were struggling to give decent glimpses at 150X on the same targets. In the MK91, even though poor seeing means the image will wobble around, it doesn't dissolve into a blurred soupy mush.

Alex (Mental) had been using his two 8" SCT's for years to make lunar sketches... thinking all was well with them, until one night I took the MK91 to his place and side by side with his scopes. It was very quickly apparent it was in a totally different league.

To his credit, Alex embarked on something which I am sure very few have attempted - he begged, borrowed and in some cases purchased a whole swag of SCT's and maks with apertures 180-200mm and critically compared the lot over several nights, and ultimately put up the best three against the MK91.

The result being an Intes M715D clearly outperformed the SCT's by a significant margin, and that scope also shows a similar response to average/poor seeing as the MK91, ie the image wobbles, but doesn't turn into mush.

A few conclusions were reached:

1. Scopes with really, really good optics are significantly less affected by seeing than scopes with average to poor optics.
2. if the collimation is off even by a tad, while you may think the image looks OK in moments of steady seeing it will be badly degraded by poor seeing, Reduced to blurry mush, basically.

It also suggests premium APO refractors (such as the AP 130GTX) behave similarly and in some respects helps to explain why some are addicted to refractors since they don't have collimation issues (assuming no-one has tinkered with the objective post-assembly).

FWIW in good seeing on Saturn, the MK91 is capable of 700X and shows the Encke division. Never mind Cassini's division, that's a walk in the park. I'm not aware of any SCT under 14" that can do that.

I know many will struggle in disbelief at this.