[ATM] Cemented Petzval

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

Here's another double cemented doublet Petzval design (150 mm f/8):

    http://users.rcn.com/rflrs/Ptz10-83x.atm   ATMOS input file
    http://users.rcn.com/rflrs/Ptz10-83x.len   OSLO input file
    http://users.rcn.com/rflrs/Ptz10-83x.txt   TEXT prescription
    http://users.rcn.com/rflrs/Ptz10-83x.zmx   ZEMAX input file

As with the others of this type, both doublets are cemented -- only
4 air-glass surfaces.  The flint glasses (S-TIM3 and N-BASF64) are
not run-of-the-mill, but not outlandish, I think.  The net weight
is under 1.7 Kg of glass and the length is about a meter and a half,
so the "cost" of the Petzval is under 28% in length -- of course,
there will be a proportional loss in color correction; hence f/8.

The e-line is well corrected, about lambda/75 P-V, so testing would
be good at that wavelength.  There is little astigmatism -- less
than 0.1 micron of longitudinal error at the e-line.  The field
RoC is roughly equal to the focal length.  Lateral color is well
matched between C and F, about 5 ppm difference.  Longitudinal
color correction is also quite close to canonical, with the C-F
crossover at the 75.4% zone.

The net result is a Visual Strehl of about 0.7 over the entire
2 degree (42 mm) field (within about +/-0.005).

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