Re: Gregory design

Steve Strickland (lensnut@tpoint.net)
Mon, 3 Apr 1995 15:32:47 GMT

>Although Gregory was first to publicly give all the details of a
>Maksutov-Cassegrain using back of a menisk as a secondary, it really
>was Dimitri Maksutov himself who has "designed" a Mak-Cass (shown even
>as early as '47 (?) in his infamous JOSA paper), together with "true"
>Maksutov and Maksutov-Gregorian. He and his Russian (sorry, Soviet)
>colleagues had made working prototypes of Mak-Cass and Mak-Gregorian in
>early forties, but design details were never published (at least to my
>knowledge).
>I'm not nit-picking, just want credits where they are due to.
>
>BTW, as far as I know, both Questar and Intes use separate radius
>for a secondary (either separate mirror, or ground-out central part of
>a corrector), so strictly speaking, they are not based on Gregory's
>design.
>

>PS I don't want to be misunderstood, I _am_ great admirer of John Gregory,
>but some things simply have to be clarified. I am sure that he would even
>do this himself, if he had a chance

Yes, I'm certain he'd want absolute accuracy, too. And thanks for clearing me up on these details. It's my understanding that while Maksutov described a Cassegrain version, he did not give the curves or performance data, which is what Gregory did. Gregory has never claimed to have invented the design, he just took Maksutov's theoretical work and engineered it into a practical model. As for the Questar, the first generation of these were Maksutov-Newtonians based upon Maksutov's original work. The second generation were Gregory-Maksutov's, based on John's work. Later versions used a separate curve for the secondary. I'm not a Questar historian, but this is what I've gleaned from my reading. Perhaps it's not correct.

It's interesting to note that most of the Maksutov development that John published has been improved, John attributes this to the development of the computer and the many orders of magnitude increase in the speed of optimizing and experimenting with optical designs. He tells me that his current G-M design is much better than the one he worked up in the '50's.

What I hope to do is get John Gregory in front of my computer and Log-On with us. He has many, many fascinating experiences to share. I hope he'll also be ready to publish some of his latest work.

--
Steve Strickland
Lensnut@tpoint.net