[ATM] UltraThin support investigation

[Dale Eason <atmpob@yahoo.com>]

Below is 3d surface analysis of David's ultrathin
mirror on what I know to be a good mirror cell for my
16 x 1 inch mirror.

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

This shows the magnitude of the support problem when
compared to the actual surface.

http://Home.comcast.net/~doeason/DDavis/3_eights_3D_Surface.jpg

I have turned off spherical aberation in both. Both
images are the same orientation.  You can see the
stand completly swamped and reversed the surface this
time.  I have others were it is in the opposite
direction and others where the cell does its job and
the real surface appears.

I tried my best to make it sit evenly on the cell. The
cell was computed by PLOP for my 16x1.  It is not the
ideal for this mirror but the best I have.  The cell
is tilted back 45 deg.  I have described the cell
before and Steve Koehler has published data showing
how just rotating the mirror creates new and different
errors.   We think the astig is induced primarily by
the lateral supports. They can not support it at its
COG because the mirror is slumped into a bowl shape. 
We think that because it is aligned and high with one
of the pegs at random times.

Bottom line is you move the mirror and the support
changes in terrible ways.

I wish I could use roller bearings for the edge
support but that is not possible since the edge is so
thin.  It would also not be on the COG but so it is
with the pegs.

I'm going to try sticking a central support on the
back once I figure out how to integrate it with my
cell or some other back support.

Dale Eason

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