[Fwd: [Raytrace] Raytracing mirror support distortions (active optics)]

[Hermit]

-------- Original Message --------
Subject: [Raytrace] Raytracing mirror support distortions (active
optics)
Date: Fri, 07 Dec 2001 12:58:08 -0500
From: Peter Chen <chen@stars.gsfc.nasa.gov>
To: <mailto:@poph-f.gsfc.nasa.gov>

Hi:

	Thought to tell the list of another project I'm interested in, although 
I'm not sure how well it will work out.   David Lewis has written an 
excellent program called PLOP which is available from his site 
http://www.eecg.toronto.edu/~lewis/.   PLOP computes the optical surface 
shape of a telescope under various support schemes (3 points, 9 points, 
multiple rings, etc).  It is an excellent program and very user
friendly.

	I thought it might be interesting to do raytracing for mirror under a 
variety of support schemes.  This is called 'active optics'.  It is 
especially applicable to large thin mirrors (a la Mel Bartels?).  
Acitve 
support is the technique used by the European Southern Observatory in
its 
four 8 meter Very Large Telescopes, currently the biggest in the 
world.  The mirrors are thin and therefore very sensitive to how they
are 
supported.  In fact, the VLT supports are cleverly designed to
compensate 
for astigmatism, spherical aberrations, and coma.

	I wrote to David Lewis some time ago, and he kindly modified a PLOP 
program to output mirror shapes in Zernike terms.  I'm trying to see if 
it 
is possible to use the PLOP generated Zernike terms and import them into 
Zemax (or other programs) and do a raytrace.  The ultimate aim, of
course, 
is to be able to adjust the support forces on a mirror to keep it at 
optimal shape during observations.
	Wish me luck.  I'll try to keep the list informed of my progress.

P.C. Chen

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