Frank Ward wrote: > Gentlemen, > > I have a 4.5 f22 Maksutov. I chose that fl with the idea of using it as > a photographic guide scope. > Now my interests have changed and I'd like to lower the f.l. > > Celestron has always offered a "focal reducer" on their long f.l. scopes to > make > them more versatile. I'd like to incorporate one like theirs in my > optical path. > > 1) What is the configuration of a "focal reducer" ? > > 2) Since it does the oposite of a barlow I would think it > would be plano convex. > > 3) Do they work like a reverse barlow, i.e. the lens itself doesn't have > to be fabricated to fit the specs of my individual scope? > > > > Second question: > > How do I compute the maximum length of a glare stop tube between the primary > and the corrector (as the Quasar people do it) To allow me to use the > scope during daylight and only let the rays from the aluminized central > spot to enter the eyepiece. Mirror and corrector separation is 12 inches, > bfl is 14 inches? > > TIA > > Frank Ward -- Clear skies, Mel Bartels http://www.efn.org/~mbartels
-- BEGIN included message
- To: atm-owner@shore.net
- Subject: focal reducers
- From: Frank Ward <thewards@mindspring.com>
- Date: Sat, 12 Sep 1998 23:22:38 -0400
Gentlemen, I have a 4.5 f22 Maksutov. I chose that fl with the idea of using it as a photographic guide scope. Now my interests have changed and I'd like to lower the f.l. Celestron has always offered a "focal reducer" on their long f.l. scopes to make them more versatile. I'd like to incorporate one like theirs in my optical path. 1) What is the configuration of a "focal reducer" ? 2) Since it does the oposite of a barlow I would think it would be plano convex. 3) Do they work like a reverse barlow, i.e. the lens itself doesn't have to be fabricated to fit the specs of my individual scope? Second question: How do I compute the maximum length of a glare stop tube between the primary and the corrector (as the Quasar people do it) To allow me to use the scope during daylight and only let the rays from the aluminized central spot to enter the eyepiece. Mirror and corrector separation is 12 inches, bfl is 14 inches? TIA Frank Ward
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