RE: [ATM] Calculate Astigmatism

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

There is a neat remedy to this problem in the old Albert Ingalls atm books,
I remember.

I will try to find it and make a post about it. I have a nice, new
replacement set of the old three volume set as a gift from a dear friend,
one of the members of this list. I will try to find that article and direct
everyone towards it. Right now I am dealing with my father, who has decided
to let himself die immediately.

Davey

P.S.- Just now, when opening my email program, I got about eight viruses,
immediately, including several of the new, self launching virus- I think it
is named "message xlt". I had to jump through closing and x-ing buttons and
no buttons like crazy to prevent it from launching Windows Media Player. Are
any of you folks getting this thing? I delete them out of quarantine
(Norton, Symantec) before I reply or send original messages; Norton
evidently quarantines them, but when one of the messages is selected (not
opened; I receive in Outlook) the thing tries to launch media player anyway,
even though I later go to Norton and see them quarantined. Can anybody input
advice about this thing?

My father may die tonight; he never wanted to have a relationship with me
(had some kind of psychological block about relating to people, and then
married a woman who forbade him to have a relationship with his blood kin).
Sorry. Off topic. I apologize.

I'll look for the article in the old Ingalls books for you guys. I'll try
to, if I can see through my tears.

Davey

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net]On Behalf Of
Woodchuck
Sent: Wednesday, March 24, 2004 1:52 PM
To: Stephen C. Koehler
Cc: atm@atmlist.net
Subject: Re: [ATM] Calculate Astigmatism

On Wed, 24 Mar 2004, Stephen C. Koehler wrote:

> > throwing away the ability to make differential measurements to the
required
> > accuracy.
>
> I don't understand the need to not disturb the apparatus over a mirror
> rotation.  Couldn't you use the measurement of the center zone on each
data
> set as a baseline, or at least make the assumption that your innermost
zone
> is not much affected by astigmatism?  This would eliminate the need to
> maintain the test rig distance over a mirror rotation.

Another alternative would be to use a pinhole, and rotate the direction
that the KE moves to intersect the image.  Horizontally for horizontal
zones, vertically for vertical zones.  If pinhole and mirror are not
moved, then one might measure on-axis astigmatism this way.  I imagine
a mask with four apertures at the edge at 12, 3, 6 and 9 o'clock.

A certain precision in construction of the KE apparatus would be needed,
though, otherwise a "re-zero" step with the central zone would be needed.
It would seem easier to construct a rotating knife edge than a rotating
mirror.  Maybe it could be done optically, with a Dove prism?

Dave

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