Jerry Warner wrote:

I think I was told once its Gregorian - note the long tube for the 4' ap at f/6.

Only the Gregorians had such low focal lengths - ???
jerry

I think that some of them did have somewhat shorter focal lengths. The
Gregorian might have been easier to make, since it used only concave optics
and these were easier to test than convex surfaces. I recall a club program
put on by Dr. Eugene Rudd of UNL (Antique Telescope Society) who brought
several of these wonderful brass instruments to our meeting. One was a 3 or 4
inch Gregorian, and although the instrument looked wonderful, I understand
that the performance wasn't all that hot. Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

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