Re: [ATM] Alternative Petzval Design

["Richard F.L.R. Snashall" <rflrs@rcn.com>]

Bob May wrote:
> Yes, a 2" EP does make a nice bit of sense for a finder.  Gives a
> much better eye relief than some smaller EP does.
Buy I assume what you meant was probably something like a
telescope that could use a purchased eyepiece, like this
(48 mm f/6, based upon Melles Griot LDX189 isoconvex and
LPK063 planoconcave lenses, that latter not still on the
MG website):

Surf     Radius   Thickness      Glass    Diameter

 STO     130.38           8      N-BK7        50.8  LDX189
   2    -130.38       0.393                   50.8
   3    -130.38           3       N-F2        50.8
   4   Infinity     179.825                   50.8
   5   103.7452         5.5     N-BAK4          48
   6   Infinity      28.128                     48
   7  -103.7452           2      N-BK7        41.2  LPK063
   8   Infinity         2.5       N-F2        41.2
   9     177.36     60.5196                   41.2
 IMA    -2525.2                              42.14

At this speed, the mismatch between the first and last
surfaces could no longer be swept under the rug.  The
eyepiece requirement is EFL*AFoV > 2400 mm-degrees --
what a peculiar dimension.
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