Re: [ATM] Higher order Null Lens for RC primary

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

Gert Gottschalk wrote:
> Hi,


> When applied to the F2.6 primary however residual
> higher order spherical aberration is no longer
> negligible. (about 0.6waves P-V)
> 
> My question. Has someone come up with a design for a
> Null-test system (2 lenses) that can be based on
> catalog lenses and is robust to tolerances for ATM use
> (kitchen table proof) ??
> 

Your information may not be quite accurate.  I hypothesized
a Ross null test, using a BK7 lens, 0.4 inches thick
against a 10" parabolic mirror with a 52 inch central
RoC.  The lens is 14.212325 inches from the source/KE
and 31.8948 inches from the center of the mirror with
radii on each surface of 52.722818 (matching the RoC
of the parabola at the edge of the mirror).

It would appear that the whole setup has a P-V error of
about 1/9 wave (e light, 546 nm).

Is it kitchen table proof?  Don't know.  Is the test
extendable to non-parabolic surfaces?  Haven't tried, yet.

> Thanks,
> 
> Gert
> 
> drgert1@yahoo.com


-- 

Rick S.

http://users.rcn.com/rflrs

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