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Gregorian Maksutov ?

Started by Bruce Mills, 12/18/2009 01:46PM
Posted 12/18/2009 01:46PM | Edited 12/18/2009 01:51PM Opening Post
As I was passing by here, a thought occurred to me (not for the first time); are there any big'ish Gregorian Mak's manufactured ?

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) ?




Posted 12/18/2009 02:35PM #1
>>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? >>

Because the distance from secondary to focus is longer, therefore the secondary must be larger diameter than with a normal Mak.

Rolando

Posted 12/18/2009 07:01PM #2
Hi Bruce,
Nice flying wing by the way...

The Meade 7" MAK is Gregorian. The Intes Micro is Rumak. Hope I'm spelling those right. Anyway that 7" scope is about as big as I've seen them.

Meade did manage to keep the size of the secondary under control, but it has some technical oddities to cope with. One being: if you do have to collimate the scope, you must move the whole meniscus assembly.

There's also a very slight cool-down advantage to the Rumak.

Steve
8)
Posted 12/20/2009 07:04AM #3
TEC offered this design for a while about ten years ago. Theirs was a Gregory Gregorian Mak with a silvered spot on the meniscus. The Meniscus was reversed BTW, with the convex side facing outward -- a very interesting little scope.

Jim McSheehy