Re: [ATM] 16" RCC primary

[Jim Burrows <burrjaw@earthlink.net>]

At 2006-01-21 17:59 +0100, Attila Schné wrote:

>But the primary is not testable in this way. I don't want to make a Hindle 
>sphere,       so I need another method to figure out when will be arrived 
>the       desired hyperboloid shape. Do you have any ideas?

For the RC primary, good ol' Foucault will work - it'll be a little bit 
hard at f/4, but possible.  Sixtests or FigureXP (I think) will give you 
the surface deviations from the desired R and b.

The hyperbolic convex secondary is another beast.  The classical method is 
the Hindle test, which is a null test IF the Hindle R is right.  If the 
Hindle R isn't quite right, the test can be run as a Foucault test (mask on 
the secondary! (I screwed up on that one)).  Whipping up a Hindle sphere is 
quick and easy - big hogging out, though - they're usually ~f/1.  I've got 
a coated Hindle sphere currently being used to do the final (I hope) tests 
on my RC secondary.  I'm willing to lend it to you if it will work for your 
system:  R = 521.7, D = 243, O = 63 (all mm) (surface RMS 0.4 nm!).

I have a couple of RC programs on my web site:
         design:  http://home.earthlink.net/~burrjaw/public/aplanat.zip
         test:   http://home.earthlink.net/~burrjaw/public/rc_atm.zip

         -- Jim Burrows
         -- mailto://burrjaw@earthlink.net
         -- http://home.earthlink.net/~burrjaw
         -- Seattle N47.4723 W122.3662 (WGS84) 

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