From: "James Lerch" 
To: 
Cc: "ATM List" 
Reply-To: "James Lerch" 


Greetings All,

While preparing for the forth coming interferometry exercises, I was idling
wondering about astigmatism, and how it may appear when testing across
three diameters.

Being the crazy fool I am, I set forth to "Criminally Destroy" a
nice 11" F/7 optic.  Basically I did everything we are told to avoid
while figuring a piece of glass.    End result, "Oh yea, I made that
puppy astigmatic!"  :)

Since I'd never really seen what this level of astigmatism  under the
Foucault knife, I took a lot of pictures and made some animations to share
with the list.
I hope you find them interesting:

Below are three animations of the mirror under the Foucault knife.  The
animations are labeled with respect to the 3 axis's I tested across (each
at 60 degrees to each other and labeled A,B, & C).

http://lerch.no-ip.com/atm/astig/A_Knife.gif (428KB animation)

http://lerch.no-ip.com/atm/astig/B_Knife.gif (429KB animation)

http://lerch.no-ip.com/atm/astig/C_Knife.gif (434KB animation)

And here's the same three axis, out side ROC, with an 85lpi Ronchi Grating

http://lerch.no-ip.com/atm/astig/A_Ronchi.bmp (230kb)

http://lerch.no-ip.com/atm/astig/B_Ronchi.bmp (230kb)

http://lerch.no-ip.com/atm/astig/C_Ronchi.bmp (230kb)

I hope you found this an interesting exercise, I know I did!

Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction,testing, and coating site)

--- BBBS/NT v4.01 Flag-4