Re: [ATM] [atm_free] RE: data and musings on thin mirror

[Jim Burrows <burrjaw@earthlink.net>]

At 2006-02-11 19:14 +0100, Nils Olof Carlin wrote:

>You need to know the distance grating to mirror vertex of course but
>not to extreme precision. Then, like any other zonal test, you know the
>zonal location on the mirror, and you know the relative position of the
>normal at a point near the COC - as you do with e.g the Gaviola test,
>and from that information you can do some integration
>(the exact method is illustrated here:
>http://www.sciencecartoonsplus.com/gallery.htm)
>and come up with a best fit curve of some kind (parabola,
>ellipse/hyperble) without knowing the ecact location of the paraxial
>COC - if any.
>
>Jim B, are you listening in?

Yup.  I'm guessing that Mel Bartels has used Ronchi something like this 
successfully for years, so it must work, maybe even with only eyeball 
reduction.  Also, Suiter, p. 296, says Ronchi can be quantified by 
recording several patterns at measured longitudinal positions, but, "... 
the test is almost never undertaken in this manner, probably because it so 
closely resembles the Foucault test that the user was trying to avoid in 
the first place."

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

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