Re: ATM Rumak Fabrication Tolerances

[Aplanatic@aol.com]

Bratislav writes:

> Hmmm... Maksutovs are notorious for false minimae, and if your
>  converging algorithm isn't up to it, you may end up manually 'nudging'
>  it for ages until you find a true best solution. I'll try your design
>  and let R1 'out' and see what my raytracer does with that. Send us the
>  numbers.

I simply used the design in Rutten and van Venrooij for an 8" f/15 Rumak.  The
design follows:

R1 -334.956 [corrector surface 1 RoC]
T1 20 [corrector thickness]
R2 -346.673 [corrector surface 2 RoC]
T2 605.8 [distance, surface 2 to primary]
R3 -1592.2 [primary RoC]
T3 -589.7 [distance primary to secondary]
R4 -598.072 [secondary RoC]
T4 832.12 [secondary to focal surface]

The corrector is made from BK7 (517642).
  
>  Before everybody jumps and starts making Mak-Cassegrain, using a phrase
>  from a local Mitsubishi car ad, "please consider" a Mak-Newtonian.
>  Tollerances are GREATLY relaxed, performance is excellent out of the
>  box (system inherently coma free), spherochromatism is even lower and
>  obstruction can be exceptionally low (0.2 and below).
>  I never understood why it was ignored by ATMs for so many years.

Can you send us your favorite design?  I would like to take a look.

Dave Rowe
Torrance, CA