Re: [ATM] Harmer-Wynne Design

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

Jens Moser wrote:
 > Hi Rick,
 >
 > great job, and this in only one day. I can't believe it.
 > I think, that the different curvatures of the mirrors is the problem
 > now. Is it possible, to design a backfocus at apx. 375mm with the f/4.85
 > Primary? The original design is a really good Astrograph, and the
 > flatness of the field is importent for me.
 >
 > Best,
 > Jens

Actually, assuming a "weak" corrector, fixing the primary and final f#'s
forces the secondary size.  Progressing from there, I was able to get
an f/4 primary.  However, it appears that about f/4.4 is an optimal
point:

	http://users.rcn.com/rflrs/Harmer-Wynne1-13x.len

The spectrum here is now properly spread out (365-1015 nm) for
astrophotography.  With the vignetting given, the % illumination is
the roughly the same across the field.

If, in fact, the f/4.4 primary is optimal for an f/8 system, you might
consider slowing down the final system to optimally match an f/4.85
primary.


-- 

Rick S.

http://users.rcn.com/rflrs


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