To: atm{at}shore.net
From: MLThiebaux 
Reply-To: MLThiebaux 


>Even if you succeed in making your off axis mirror I wish you much luck in
>repeatably being able to mount and test them.  I have accquired two 10.5"
>diameter F # 5 ish off axis mirrors professionally made by ITEK.  For the
>life of me I cannot figure out how to interpret the astigmatic on axis
>images to give me a clue as to which direction off axis to move in to find
>the true central axis.


I would start by getting at least a rough indication of the directions of
the principal curvatures. Try examining the image of a pinhole source with
an eyepiece (with source and image as close together as possible).  The
major axis of the inner elliptical image would be  parallel to the diameter
passing through the paraboloid axis (true central axis).

Martial Thiebaux
Rawdon Hills, Nova Scotia

--- BBBS/NT v4.00 MP