[ATM] flex mirror link

[Bob May]

The clamp process has been documented in the amateur press in the
last ATMJ.  Guy did an off-axis paraboloid by stressing a piece
of glass with some dimple arms glued to the back of hte glass and
weighting them with jilk jugs filled with an amount of water.  He
did a beautiful job of the whole thing and the article seemed to
be quite complete.  You're probably going to have to find a paper
copy of the ATMJ for that article but it is there.
The simple pushing of the sphere is a fair bit simpler than
calculating and stressing the mirror with this off-axis surface
shape.
One thing to note about off-axis mirror setups is that the
eyepiece needs to be pointed at the center of the revolution of
hte parabola, not the center of the mirror.  I've got a 5" mirror
that has been put into a scope and the center of the axis of
revolution of the mirror is about 11" off from the center of the
mirror.  Makes for an interesting scope and when the EP is
pointed at the center of the mirror, the focus shift is quite
obvious as the top and bottom are out of focus but there is a
band of focus from side to side in the view.  Also, due to the
short FL, EB abberations are quite obvious!
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net