[ATM] Refractor perscription

[tomjan at ozemail.com.au (Thomas)]

Richard,

First off thanks for taking a look!

Yep, my bad R1 is the positive and R2 and R3 are both negatives. really
should proof read my posts before sending them out to the real world.

Nice to hear that the two results that I got for the EFL have a reason, your
Zemax EFL is close enough to theOSLO one to be taken for real;)

No I'm not optimising it for anything other than visual work, the glass
thickness are just what I got in the box yesterday. Personally I think the
flint is very thick, but I don't know what the glass was originally ordered
for...

Anyway could you let me know what the aberations look like, and most
importantly is the design workable;)

Thanks.

Clear Skies,
Thomas Janstrom
http://www.tjanstrom.com
http://www.norsewines.com.au
----- Original Message -----
From: "Richard F.L.R. Snashall" <rflrs@rcn.com>
To: "The Amateur Telescope Makers List" <atm@atmlist.net>
Sent: Tuesday, February 03, 2004 5:47 PM
Subject: Re: [ATM] Refractor perscription


>
>
> 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
>
>
> --
> ------
>
> Rick S.
>
> http://users.rcn.com/rflrs
>
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