[ATM] what causes coma?

[burrjaw at earthlink.net (Jim Burrows)]

At 2004-02-10 08:24 +0100, Hugues wrote:

>Can an optical guru ;-) confirm? Jim Burrows, Bratislav, others?

G.D. Roth, "Compendium of Practical Astronomy", Vol. 1, ISBN 0-387-56273-7 
has an explanation (with plenty math) of the 5 Seidel aberrations: 
spherical, coma, astigmatism, field curvature, and distortion.  It turns 
out you calculate the 5 for each spherical surface and the 5 for the 
deformations (b<> 0) of each surface, then the system Seidel aberrations 
are found by adding.  P. 69 has a nice table of examples, but it was too 
difficult to copy (tabs don't work very well in e-mail).  Anyway, a sphere 
has all 5, adding the parabola's contribution cancels out the spherical, 
but leaves the other 4 unchanged.

         -- Jim Burrows
         -- mailto://burrjaw@earthlink.net
         -- http://home.earthlink.net/~burrjaw
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