BTW, I don't mean the late, great, John Gregory here. I mean James Gregory, the 17th century Scot.
I bought a little Russian 40mm aperture Greg' Mak' several years ago, and I was tickled by the ortho', right way up and right way round viewing which the Greg' gives. Which led me to wonder why there aren't any of them about, that I'm aware of, in useable astro apertures. And if not; why not?
Is it technical? Economic? Or nobody's thought to try it, maybe?
In the S&T reprint of Maksutov's original paper there's a nice photo of his prototype meniscus system, which is Gregorian(..must dig that out again!). And, wasn't Bouwer's binocular a Gregorian also? I forget. So why, therefore, have all subsequent Mak's since seem to have been Cassegrain and Newt' systems? In the case of the Cass', is it only because the tube is shorter, or something deeper than that (a better corrected system, say) ?