Marc R. Reinig wrote:
Actually, the readout rate shouldn't be a problem. You don't need that
much resolution, a 5 X 5 pixel array should suffice and you don't need
100 X 100 sub aperatures, fewer should be fine, so a smaller camera
array or binning would do. In any case, I suspect that the processing
is what is going to be more of a limit.

Right. Myabe you only need a dozen or so sub-apertures. Correct for
Tip/Tilt/Defocus with four actuators.

So I need:
beam splitter. 4-hole Hartman mask. 4 small lenses to direct the
(roughly) focused images onto the edge of a CCD. read the 8(ish) edge
lines of the CCD. get the centroids. do the calc. apply the signal to
the actuators.

A Hartmann mask shouldn't be too hard or expensive to build. I haven't
heard of any inexpensive Shack-Hartmann arrays available, though, but
there may be some coming. However, with the moon or sun I would think
it should be possible to use just a Hartmann mask.
How do you keep the images from overlapping at the CCD ?

Has anyone done a simple deformable mirror? I think that might be the
real tough one.
There were some people making scanning electric-force microscopes using
a piezo-speaker to point the probe. Maybe epoxy a mirror to a suitable
modified piezo-speaker ?

Eric.