I recently acquired a second hand Pan Tilt mechanism from a CCTV camera system.
Of special importance was that the unit used Stepper Motors to drive the two axis’ and it uses a 12 way slip ring for electrical connectivity. These stepper motors are each 200 pulses per revolution and are geared 10:1 to the axis, this gives a total of 2000 pulses per revolution, which is 0.18 degrees, or 10.8 arc minutes. I’m hoping to be able to drive the stepper motors at 1/4 stepping, which will give me 2.7 arc minutes of position resolution. The slip ring means that the Pan axis can turn continuously and the wires will never get “tangled”.
The unit is also designed in such a way that a small camera and lens assembly can be fitted so that it pans and tilts around the “nodal point” of the lens. This means I could potentially build myself a high resolution, heavy duty Gigapan.
I’m not 100% sure of the final details yet, but I hope to be able to drive the pan tilt (and possibly lens zoom and focus) by a computer. I have another project planned which uses an AVR to overlay a very accurate time stamp (and possibly RA/Dec) onto a composite video signal.
I hope to have the whole unit up and operational by March/April 2011 in time for the next launch of a Boeing X-37.