The FAQ section was written by Bill Kelley
1.Q. What is Flex?
A. Flex is a method of forming a sphere into a parabola by
mechanical
forces applied to alter and control its shape.
2.Q. Why Flex?
A. It is easier to make a sphere than a parabola. The common Foucault
test for telescope mirrors produces a null for a sphere with the surface
featureless. A parabola presents a "doughnut" shape that must be produced
by careful polishing and testing different zones on the mirror. For many
the most difficult and onerous part of mirror making is parabolizing.
3. Q. What advantages do flex present?
A. A smoother surface, ability to figure the mirror by star
testing,
easier to make, alter the figure for changing temperatures, easy to
test,
the polishing process automatically produces a sphere.
4. Q. Can some surface shape on a mirror other than a sphere be flexed
to a parabola?
A. Any conic section can be flexed to a parabola. Aspheric
shapes
other than conic sections would pose a problem of distributing flex
forces
that we have not addressed. Badly corrected shapes are not good
candidates for
flexing- flex doesn't fix bad mirrors. Nor can you flex an ordinary
piece of window glass to a useful parabola. Flex allows you to produce
a fine
paraboloidal mirror by applying properly distributed forces to a high
quality sphere. A description of how to do this was published in Sky
&
Telescope Nov. 2000.
5. Q. Is this for real? Is anyone making these?
A. Telescopes with flexed mirrors are being made by amateurs in
many places in the world, and spectacular imaging capabilities are
being
reported.
