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

["Jerry" <wa4guu@verizon.net>]

Hello Steve


Dale's Ronchigram shows three lines and white at the left and right edge. A
guess has to be made of how far of the edge the next band would be but it
looks like it would be close on each side. So I estimate 3 and one half
bands showing on the mirror.

Now I estimate how many bands could fit on the mirror if they were all the
size of the three bands in the center spherical area. I would say 6.

To show 3 Ronchi bands the COC would be half the distance from the grating
as the COC that would show 6 bands. Dale stated the grating was .150 inch
outside of center of curve. 1/2 X .150" = .075 Inch. 

With the simulated Ronchi I estimated a 3 to 5 ratio. In this case I used
the ratio of widths of the central band at the edge compared to the center,
which is the moral equivalent to estimating how many bands are on the mirror
and how many could fit if they were all as small as the ones in the center.
Dale's Ronchigrams chopped the top so it was harder to judge the width of
the center band at the edge. Anyway, with the simulated 3 to 5 ratio and the
5 being the .150 inch, would make the 3 = 90. So the difference between them
is .150 - .90 = .060"

They are estimates. I did not get the caliper out. But I can't be far off.
Certainly close enough for early parabolizing.

Jerry 



-----Original Message-----
From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf
Of Stephen Koehler
Sent: Monday, February 06, 2006 3:59 PM
To: atm_free@yahoogroups.com
Subject: Re: [atm_free] RE: [ATM] data and musings on thin mirror

Jerry,

> By the Ronchi I had estimated the correction center to edge would
correspond
> to Foucault knife movement of .075 inch with a fixed source tester. That
is
> about 10 percent of the desired .579 inch.

How did you get this estimate for the knife movement from Dale's single
image?
I forget if he specified the stage position relative to paraxial focus.

--
Steve Koehler



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