From: "Richard F.L.R. Snashall" 
To: ATM 
Reply-To: "Richard F.L.R. Snashall" 




Richard F.L.R. Snashall wrote:
 >
 > Yes, yet another design:
 >
 >     http://users.rcn.com/rflrs/jflat2-06x.len
 >
 > By reducing the requirement for an really flat field,
 > a slightly different geometry results.  Still has
 > a Strehl ratio of 0.955 (better photopicly and
 > scotopicly) and the field is still relatively shallow,
 > at 1.5 times the focal length.
 >
By reversing the field lenses, I was able to both coerce out the air space
and make the curves generally shallower.  In spite of the residual lateral
color, the Strehl ratio is still relative flat and better than 0.95 over
the field.  Tolerances seem to be looser too!

        http://users.rcn.com/rflrs/jflat3-06x.len

The glasses S-BSL7 and S-NSL5 are the Ohara "equivalents" to
Schott BK7 and K5, respectively, but slightly different, and result in
better correction.  Ohara S-BSM2 should not be substituted for SK2,
however, as it degrades it too much, but N-SK2 is a direct substitution
without re-optimization.

        Rick S.


 >     Rick S.
 >
 >
 >
 >

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