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




Richard F.L.R. Snashall wrote:
 >
 > Two examples of triplets with a split field corrector
 > are given.  Each is 150 mm f/8 with a 42.8 mm flat field
 > (big enough for a 2" eyepiece or 35 mm film), and a BFL
 > forced to 225 mm (allowing enough space for whatever).
 > Two of the less expensive Lanthanum glasses are used.  These
 > have approximately the same refractive index.  This would
 > allow for the same index matching oil to be used on both
 > sides of the central Fluorcrown.
 >
 >     http://users.rcn.com/rflrs/calcn-27x.len
 >     http://users.rcn.com/rflrs/calcn-30x.len
 >
 > The first is optimized for Photopic use, while the
 > second is optimized for Photographic use.
 >
 >

OOPS.  Almost forgot people are into CCD's these days (requires a bit more
BFL, but is actually shorter overall):

        http://users.rcn.com/rflrs/calcn-31x.len



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

--- BBBS/NT v4.01 Flag-5