Re: [ATM] Simple Petzval Design

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

Richard F.L.R. Snashall wrote:
> A 150 mm f/7.5 Petzval design:
>
>     http://users.rcn.com/rflrs/Ptz07-79x.atm
>     http://users.rcn.com/rflrs/Ptz07-79x.len
>     http://users.rcn.com/rflrs/Ptz07-79x.txt
>     http://users.rcn.com/rflrs/Ptz07-79x.zmx
>
> Only four air-glass surfaces.
>
I happened on the website of S.I. Howard Glass
(  Welcome to S.I. Howard Glass <http://www.howardglass.com/home.htm> ) 
that has 17 mm thick (=/-0.5 mm)
B270 glass (they're actually just down the road a bit).  They
are not listed on the ATM resource list, so I don't know if
they'll deal retail to ATMs or not.  Also, looking at the Ohara
US site, the stock minimum width of S-TIM28 is 160 mm,
so (220 mm f/7.5):

    http://users.rcn.com/rflrs/Ptz08-50x.atm   ATMOS input file
    http://users.rcn.com/rflrs/Ptz08-50x.len   OSLO input file
    http://users.rcn.com/rflrs/Ptz08-50x.txt   TEXT prescription
    http://users.rcn.com/rflrs/Ptz08-50x.zmx   ZEMAX input file

The OSLO and ATMOS files have direct specification of B270
refractive indices (assumes the ZEMAX values are correct).
Assuming the quality and RI is good enough, the expansion rates
within each doublet are quite close (exact on the larger one),
so there is probably little expansion problem here.

Again, this is corrected for spherical aberration, coma and 
astigmatism.  Both lateral
and longitudinal color are quadratic over C-F.  The longitudinal C-F 
crossover is
at the 70% zone.
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