From: "Richard Klappal" 
To: "Jim Burrows" , 
Reply-To: "Richard Klappal" 


I haven't been plying real close attention to this discussion, and maybe
the equation answers it, but I've wondered what affect the 'parallax error'
between the mask and the true glass surface is.  The outer radius of a zone
AT THE GLASS is not the same as the radius AT THE MASK, especially at
larger radii.

It's simple enough to calculate, but the original Texereau program didn't
have a correction.

Maybe its not really worth the calcs, but if someone already did, I won't
have to dredge the trig out of my mental cobwebs.


Rich



-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of Jim
Burrows
Sent: Saturday, July 05, 2003 00:58 To: atm{at}shore.net
Subject: Re: ATM Robo-Foucault, the "Fresh Start" is in progress! :)



At 13:14 2003-07-04 -0500, Michael Peck wrote:

>s_m ~= sqrt [ (.03)^2 + (.7/4F)^2 * 2^2 ] ~= sqrt [ (.03)^2 + (.04)^2 *
>2^2 ] ~ 0.084 mm
>
>This is just a back of the envelope calculation but it's within 10% or so
>of what my models return. What it says is the dominant source of random
>errors in your data isn't your Foucault readings but instead is the
>limited spatial resolution of your images.

I've always had the intuitive suspicion that zone radii errors were
Robo-Foucault's Achilles' heel.  I think the above result also yells
PINSTICK or maybe even  a MASK to fix the zone radii instead
of fiddling with center estimates, edge circles, and pixel balancing.

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

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