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Re: ATM Budget ED triplet




Richard F.L.R. Snashall wrote:
 >
 > Now that I have a copy of the Ohara catalog, I can
 > wander a bit more.  Simple oil-spaced triplet with
 > FPL51 and two cheap crowns.  (150 mm f/9)
 >
 >     http://users.rcn.com/rflrs/ed_trip1-09x.len

However, when I allowed an air-space, and (depending
upon the field and optimization goals, I think) choosing
an f-ratio between f/11 and f/13, the inner two
radii can be made equal:

	http://users.rcn.com/rflrs/calcm-66x.len

Although the air-space is fairly small ( < 1 mm ), the
ghost spot is 8-10 mm in diameter.

-- 
Rick S.
http://users.rcn.com/rflrs