From: "CSC" 
To: "Atm" 
Reply-To: "CSC" 


Good question.  There was talk on this earlier.  Arthur Leonard wrote an
article, "Collimation tolerances for reflecting Telescopes" found
in Mackintosh's ATMT vol 2, pp100-109 that discusses the abberation
contribution of this error, and shows it depends mostly on f/#.  He says
that to avoid this abberation, the "edge error" or the centering
error you call it needs to be:
F/10  .2"
f/8     .1
f/6     .05
f/5     .027
f/4     .014
f/3     .006

This is the amount he calculates for 1/8 wavefront error.

As you imply, this error is different than angular collimation error, and
if present will not collimate out, and gives the appearance of a warped
mirror. He says it's more common when there are many figuring steps.

Colin






-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of Poul
Linnet
Sent: Saturday, December 14, 2002 11:14 AM To: atm{at}shore.net
Subject: ATM Parabola center



After reading Nils Olofs excellent article on collimation in S&T Jan
2003, I began wondering whether a marking at the physical center of the
mirror blank always corresponds to the center of the parabola  within 1 mm
as required for proper collimation?

Poul Linnet

Email:             poullinnet{at}city.dk
Homepage:     http://poullinnet.homepage.dk

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