>      A presume a slide projector does not accomplish your goals because it
>      doesn't create a moving image.

Actually, this just reminded me of another planetarium trick....

If you place a pair of rotating back-to-back first-surface mirrors in
front of the slide projector, the image is made to slew across the
projection field.  You need to use first-surface mirrors (available from
Edmund Scientific) or you will have a double reflection - the primary off
the silvering, and a faint one off the glass face.

By using the mirror-mount as a cam, you can trigger a microswitch to
advance the slide projector once per half-revolution.  This will call up a
new image each time the slide slews across.  We have used Hurst syncronous
motors (usually the reversable ones, as they tend to have more torque) to
drive the mirrors.

Best results will probably be with Kodalith film - a graphic arts film
that is either black or white, with next to no greys.  You can check
specialty photo labs for it.  If you need to develop it yourself, it is
simple to do (and *very* forgiving).  Kodalith has no exposure latitude,
so I'd bracket your shots....

One final trick is to tuck a slide into the gate of the projector before
putting the tray on.  The tray is cut out so that the 'zero' slide can go
into the tray, but you can't drop it in from on top.  By doing this, you
never have a blank.

-j