Re: [ATM] 22" F/4 primary, F/6 system

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

Dominic-Luc Webb wrote:
> I deleted the original post, but have it in memory. I long ago
> tried such designs and often had problems getting decent spot
> diagrams. I suspect this is why so many of the designs have
> higher amplifications. I see some real hardships in producing
> anything but a spherical primary much below F/4 (I have some
> plate glass F/3 mirrors I am struggling to get spherical, let
> alone any more complex conics).
I was able to get a design (not quite as good, but respectable)
for a corrected PC.  But then, the amount of figuring on the
secondary was aggravated (conic near 20 on a secondary c. f/5.4)
and ended up being about twice the physical departure from a
sphere that is on the primary of the corrected DK.
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