From: "Richard F.L.R. Snashall" 
To: atmlist 
Reply-To: "Richard F.L.R. Snashall" 




Bob May wrote:

> RoweTrace tends to indicate that this is a good set of numbers for the BSC2
> and SF12 glasses.  Anybody got better numbers for this?  I'll note that the
> results tend to indicate to me that there may be a need to parabolize a
> surface to reduce spherical aberration.

I just went back to Roger Ceragioli's refractor design page and found
mention of shifting the minimum focus in a doublet design.  Borrowing from
Matt Considine's Vacuum Pan Calculator html, I was able to come up with a
calculator for the G-sum program that allows for shifting the minimum
focus.  I tried it with BK7 and F2 at both d (587.6 nm) and e (546.1 nm),
but the minimum focus was 15.3 and 10.4 nm, respectively, shifted toward
the blue from the desired values.

Does anyone know the internal workings of the G-sum program enough to be
able to tell me why it might be shifted that way?

        Rick S.

BTW: If anyone's interested in this, maybe I can put it on my web page...
but, since I stole so much of the GUI stuff from Matt, I'll have to wait to
get his permission before putting it there.

--- BBBS/NT v4.00 MP