[ATM] Refractor perscription

[rflrs at rcn.com (Richard F.L.R. Snashall)]

Thomas wrote:
> Hi all,
> 
> I have just been working on a design to use some of the optical glass that Guy Brandenberg was offering last year.
> 
> Just to freshen everyone's memory heres what we know about the glass....
> 
> Vintage 1950's approx anyway.
> The crown is listed as BSC with an n # of 1.517 and with an Abbe # of 64.5
> The flint is stamped F620 with in pencil 620 and 36.2 the last is most likely the Abbe # the first short hand for the n # of 1.620
> 
> Both elements have a diameter of approx 5.5" with the crown having an edge thickness of .45" and the flint having an ET of 1.05" 
> 
> Anyway with all that said here is the design that I came up with today, I know there isn't really enough info for a really detailed analysis of this design, but it would be good if some one would be kind enough to run the numbers through a non OSLO package. (I have OSLO lt )
> 
> R1  -716.34mm
>                         Crown (finished thickness estimated 11mm)
> R2  1074.51mm 
>                         Air 1mm thickness
> R3 -1074.51mm 
>                         Flint (finished thickness estimated (26mm)
> R4  6569.28mm
> 

Given that R2 is really supposed to be -1074.51 (matching R3, maybe)
ZEMAX model glasses 1.517,64.5 and 1.620,36.2 give a focal length
of 1871.5162 mm at 555 nm, or f/14.94 for a CA of 125 mm.

I would note, however, that the typical GSUM treatment would come
up with a significantly different answer at f/15 (given the glass
parameters and thicknesses you provided).  Are you optimizing for
some really unique purpose?

> OSLO gives an EFL of 1880mm, but my calculations gives me 2095.63mm.....
> 
> So I have an F/d of between F/14.8 and F/16.5 the final ratio will depend some what on how much lens' edge the cell will use for edge support.
> 
> Anyway there it is.
> 
> Clear Skies,
> Thomas Janstrom
> http://www.tjanstrom.com
> http://www.norsewines.com.au


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Rick S.

http://users.rcn.com/rflrs