[ATM] Lateral mirror support test cases measured with interferometer

[Tom Krajci]

>From: Dale Eason <atmpob at yahoo.com>

>...I measured my 16 x 1
>plate f5 mirror with my interferometer to see the
>difference between lateral supports of two pegs at 45
>degrees from the bottom center and only one support at
>the bottom center....

>...I have a more detailed analysis of my earlier lateral
>testing.  I discovered that what I had measured was
>not the difference between two and one peg support.
>The difference was created more by the placement of
>the contact point in relation to the center of mass of
>the mirror edge.

>http://doeason.home.comcast.net/lateral_test/lateral_support.pdf

Thanks for the photos in this document!  They show where the lateral support
is placed relative to the mirror's edge (center of mass) in various tests.
But they don't show the forces being applied by the lateral support(s).  I
can assume that the force applied is normal/perpendicular to the mirror's
edge...but I can't be certain because this support setup probably can apply
force that is not normal to the mirror's edge...thanks to the shape of the
support, and the presence of friction between the support and the mirror
edge.

This is why I advocate edge supports that are more like:
http://astrosurf.com/altaz/lateralsupport.htm
When made, and used properly...these kinds of supports will apply force
perpendicular to the mirror's edge (which is what we want)...and apply very
little force in any other direction (which is also what we want).

Another option, suggested by Andy Saulietis, is to use some sort of sling
that's made of rollers/balls (like you find in old light bulb
pull-switches)...this sling can't apply forces that are parallel to the
mirror's face...or it would roll off the mirror's edge!  It can only apply
forces perpendicular to the mirror's edge.

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Tom Krajci
Cloudcroft, New Mexico
http://overton2.tamu.edu/aset/krajci/

Center for Backyard Astrophysics (CBA)
http://cba.phys.columbia.edu CBA New Mexico

American Association of Variable Star
Observers (AAVSO): KTC http://www.aavso.org/
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