[ATM] Ronchi Movie of the ultra thin mirror and other ramblings.

[Dale Eason <atmpob@yahoo.com>]

For David Davis' 16 x 3/8 mirror I
made a movie while moving the ronchi platform.  Screen
is 100lpi.  It starts outside ROC and move to inside
ROC.  The zoom lens on the camera vignettes outside
ROC but not too bad to see what is happening.  

http://home.comcast.net/~doeason/DDavis/ronchi_100lpi.mpg

File size is 173K.

I'm not looking for info on how to figure this mirror.
 It is not mine.  I'm just measuring it.  My
interferometry analysis was previously posted

http://home.comcast.net/~doeason/Analysis_of_Davis.htm

I thought some might find a ronchi movie interesting
and be able to compare it to my interferometry
analysis.

The mirror is vertical on David's mirror cell.  The
astigmatism is 45 to vertical.  There are areas where
the mirror could be improved.  My purpose in posting
some much is in hopes that David Davis can learn how
to see, measure and control it while he is figuring
such thin mirrors.  David previously thought the
mirror was much better than I measured it.  So either
the mirror has changed over time,  my measurments are
wrong, or his were wrong.  We both are trying to work
that out.  I belive mine are accurate.  David will try
measuring again to see.

About the only test system David and I have in common
that can see astig is Ronchi. Thus I have taken ronchi
images and made the movie so that hopefully we can
compare over the net.  Part of that was to ask the
list how many of you could see the astig.  I don't
know how to read ronchi and thought it might not be
sensitive enough to see the 1/2 wave pv on the surface
of astig.  Indeed, not many quantified it.  Only Mel
so far.  In all fairness not many need to have that
skill.  Most mirrors are thicker and little extra care
is required to avoid creating astigmatism.

David's goal is to make extremely cheap and light
weight telescopes that he gives away to school
children to foster an interest in astronamy.  They
only need to give good low power views of the moon for
the most part.  So his requirement is not as stringent
as some of us perfectionists.  

Dale Eason

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