This heliostat was built by Josema of Spain. The machine itself is controlled by the Arduino Sun Harvesting Program featured here on Cerebral Meltdown.
You may have noticed that the mirror is mounted on top of a solar panel. This is because this heliostat also doubles as a sun tracker! Here is a quick video he made of it switching between heliostat and sun tracking mode.
Josema reports that the machine has great tracking accuracy due in large part to the worm gears he is using. These worm gears were originally used to move the power windows in cars. If you are interested in designing / building your own machine, this type of worm gear would be a great starting point.
This next picture shows Josema’s DIY electronics circuit wired together, which appears to be quite similar to the circuit used in the Arduino Sun Harvester Shield. Very Cool!
You can find more pictures of Josema’s heliostat on his blog. (The link should go to the Google translated version.)
You can also find his forum post on this site here.