Re: [ATM] Ronchi testing

[buck childers <bchilders@everestkc.net>]

Have you taken a look at this page:
http://www.atm-workshop.com/ronchi-test.html

If you look at the sample graphics about midway down the page they show
the progression that you'd see in the lines for several shapes.  You
should be able to get a sense of which shape you have by matching what
you see as you go inside to outside with one of the sets.  For now don't
worry about how much the offset is, just look for how the lines change
going from inside to outside.  You should be able to tell if you're
dealing with an oblate ellipsoid (under-corrected) or a hyperboloid
(over-corrected).

-Buck

----- Original Message ----- 
From: "Jerry B. Hillman" <JBHillman@ev1.net>
To: "The Amateur Telescope Makers List" <atm@atmlist.net>
Sent: Sunday, May 09, 2004 10:38 AM
Subject: [ATM] Ronchi testing


> Hi all,
> I have a stupid question but I am so frustrated I can't think
straight.  I
> have given up on Foucault testing for now.  The results I get vary so
widely
> that they don't make sense.
> The ronchi test shows that at ROC I don't have as many lines as I
should.  I
> have to go inside of ROC to begin to get a matching pattern.  I should
know
> what this means but I need help.
> Does this mean that I am hyperbolic? (lines curving too much?)  When I
> adjust the conic value, I have to set it to about -.32 to get a
matching
> pattern at ROC.  This would seem to indicate that I am on the
spherical
> side,  But then working with negative values has always messed with my
mind.
> Is -1.0 more or less parabolic than -.32?
> Sorry for the stupidity,
> Clear skies, Jerry
>
>
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