[ATM] Re: ATM: Next Moves

["David Harbour" <scarab2@cox.net>]

Oliver,

May I say that I have never seen sharper focographs, better looking
focographs, more information-conveying focographs, than yours.

I want to offer you what may be a very ("relatively") painless remedy for
this turned down edge. First you must make sure to answer one question for
me, and be certain of your answer:

Does your knife edge move in, laterally, from the RIGHT, as the indications
in your focographs show that it must, for you to have this turned down edge,
or does your knife edge move in from the LEFT , in which case your
indications are for a narrow TUE.

Also, let me know if you have a broadband connection or not (not necessary;
only slightly more convenient).

I fought TURNED UP EDGE, furiously, for years- even trying to get a turned
down edge, on purpose (by design) to defeat getting a sharp TUE that was
wide, but had a very non-linear shortening of ROC the closer the zone
measured was to the edge.

Strangely enough, TDE and TUE are not entirely opposite defects; they both
represent a zone with a CREST. It just so happens that the crest on a turned
up edge is located (its "crown") right on the edge of the mirror; whereas,
the crest on a turned down edge is a little further in, MAKING IT EASIER TO
TREAT. Let me know for sure whether your K.E. comes in from the left, or
right, for certain.

The sharpest, most detailed focographs I ever saw, until yours, today, were
made by Texereau of the primary mirror (and secondaries, photographs
technically not focographs, because they used a star, and a guided exposure
at Cass. focus with a razor blade, they were essentially the same thing)-
perhaps we might call one of them a "null-o-graph"- these were published
about in the early or mid sixties in Sky nd Telescope, when he refigured the
secondaries of the venerable old McDonald 82"; well, yours are even more
contrasty and sharper than those. Well done.

Let me know; right or left, for the lateral movement of your K.E., and then
I think I can send you something (with illustrations) that will give you
much quicker relief than the old, traditional, tedious methods.

Beautiful focographs!

David

P.S. I am sorry to say that I only ever knew one foreign language (not your
native tongue) and so I could not entirely decipher the captions along with
each very excellent focograph. For this cloddishness, I apologize.


----- Original Message ----- 
From: "Oliver Kersten" <oeli@comesso.de>
To: <atm@atmlist.net>
Cc: <oeli@comesso.de>
Sent: Tuesday, May 03, 2005 4:31 AM
Subject: [ATM] Next moves


> Hi all,
>
> I'm still fighting a TDE on my 10" F5.5 and try to reach a sphere. I've
put my
> latest Foucault images under
>
> http://www.comesso.de/oeli/atm/mirror/mirror.html
>
> I think the shape gets better, but very very slowly.
> Once again, I would like to ask for any suggestions for my next moves...
>
> Greetings, Oliver
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
>


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