[ATM] Reuse

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

In his talk at Stellafane, Richard Parker presented a design
adapted from the Newport Glass BK7/F4 Fraunhofer.  In this
design, the inner radii were equal.  This allowed one of the
surfaces to be tested by interference against the other.
cf:

 http://www.stellafane.com/post_conv/2005_conv/2005_conv_2.html#shorttalks


I presented an intermediate design with higher visual Strehl.
cf:       http://astro.umsystem.edu/atm/ARCHIVES/DEC05/msg00014.html

I have reworked this design.  The result is pretty much equivalent.
When this rework is scaled to use the 8" Newport Glass doublet,
it is:

Surf     Radius   Thickness    Glass   Diameter

 STO   Infinity   -2.920433               203.2
   2    1768.76       21.28    N-BK7     208.28
   3   -1086.22        9.76              208.28
   4   -1086.22       15.08       F4     208.28
   5    -4940.4    3006.816              208.28
   6  -1090.756      ~0.165                  42
 IMA  -1090.756                              42

Another alternative is to adjust the air-space and add an
air-spaced N-BK7/F4 Littrow doublet to make a f/10.43 Petzval:

    http://users.rcn.com/rflrs/Ptz08-65y.atm   ATMOS input file
    http://users.rcn.com/rflrs/Ptz08-65y.len   OSLO input file
    http://users.rcn.com/rflrs/Ptz08-65y.txt   TEXT prescription
    http://users.rcn.com/rflrs/Ptz08-65y.zmx   ZEMAX input file


The diameter of the Littrow doublet lenses is chosen to be the
same as the 4" Newport Glass Fraunhofer doublet.  Maybe there
is some savings to be had there, as well.

Note the radii of curvature on the Littrow doublet.  Provided
these are made before the larger lens is AR coated, the curved
surfaces can then be figured against mating surfaces of that
larger doublet.
   


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