Re: [ATM] 18 point cell and ultra thin mirror.

["Scott Milligan" <starzkey@charter.net>]

My first thought on this subject is that mirrors with aspect ratios
approaching 40:1 will require some form of active support (i.e. actuators,
wavefront sensor(s) & feedback).  Even if a mirror mount succeeds "by
design", when executed in the "real" world, phenomena like friction,
stiction, compression set, geometry errors, (etc. add your own list) that
are difficult to model accurately will degrade performance well below what
the model predicts.  

But of course, I have never actually attempted to mount such an ultrathin
mirror myself, so perhaps someone on this list will succeed and prove my
first thought wrong.

Scott Milligan
 
 
-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
Dale Eason
Sent: Saturday, February 11, 2006 2:17 AM
To: atm@atmlist.net
Cc: atm_free@yahoogroups.com
Subject: [ATM] 18 point cell and ultra thin mirror.

I thought my 18 point cell should do better than the
wood and rubber mat.  Here is an image with the same
scale.

http://home.comcast.net/~doeason/DDavis/18_point_cell.gif

Surprise it is worse than the rubber pad. However most
of its error is astigmatism.  I think the mirror is so
light (5 lbs) that it does not let the wiffle tree do
its jog.  Perhaps I did not build it with enough care.
 Here is a web page show it in more detail.

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

here is the cell with a clear mirror in place along
with the tap support.

http://home.comcast.net/~doeason/DDavis/cell_tape_support.jpg

Any thought are welcome.  Steve Koehler is make a
composit image of my cell and the error.  That way we
may be able to see some correlation.

Dale Eason

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