Re: ATM An $18.00 Null Test

[Bradley Davy <bdavy@fred.net>]

I searched the archives for Fresnel, but came up with zip regarding this
question.  Please point out any errors with this theory.  For a null
test on a parabolic mirror, one needs parallel light rays.  Optimally,
the star test achieves this, but atmospheric problems limit the ability
to conduct this at the convienience of the mirror maker.  Could a
Fresnel lense (such as from an overhead projector) be used to produce a
parallel light source to test smaller mirrors?  It makes sense to me
that the lense could be placed reasonably far away in a basement,
combined with a bright light source (laser pointer and pin hole) to
effectively create an artifical star.Has anyone ever tried it? 

-- 
Brad
bdavy@fred.net               http://www.fred.net/bdavy/home.html