Re: [ATM] Alternative Petzval Design

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

Richard F.L.R. Snashall wrote:
> 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):
The same first lens could also be used in a simpler form
(48.8 mm f/6.3):

Surf     Radius   Thickness    Glass    Diameter

 STO     130.38           8    N-BK7        50.8
   2    -130.38       0.425                 50.8
   3    -130.38           3     N-F2        50.8
   4   Infinity     185.968                 50.8
   5     99.093         5.5   N-BAK4        46.4
   6   Infinity       26.95                 46.4
   7    -99.093        3.46   N-BAK4        38.6
   8     130.38     61.8681                 38.6
 IMA     2296.3                         42.28714

With the longer focal length, the field here is just under
eight degrees.

BTW, I did find that lens, or something quite similar, on
the Surplus Shed site for $8 (PL1012 -- 127 mm f.l. N-BK7).
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