Just finished the hardware part of the control board for the camera mount. I'm using a 7.2v NiCAD RC car battery to power the whole thing. Conveniently, the EasyDriver board I'm using (the red board mounted on headers to the microcontroller board) has a 5V output that can be used to power the microcontroller, so that saves my throwing down a regulator and a bunch of caps. For sanity's sake I put a rectifier diode between the 5V output and the microcontroller's VCC pin to ensure that nothing is driven the wrong way when i'm using the ISP header to program the microcontroller.
The code and hardware work well but the driver chip on the EasyDriver gets very hot very quickly, so it'll definitely need a heat sink on there when running it for long periods. I might even mill out an aluminium case in such a way that the case itself forms a heatsink which should work well in the cool nighttime air.
Next job is to figure out what the input:output turns ratio is for this gearbox. And also design the mounting plate that will let me attach the stepper to the gearbox.
Annoyingly, the worm screw that I epoxied to the stepper shaft didn't set straight, despite my best efforts to align it. There's about 0.25mm of deflection at the worst position in the stepper's travel. I will probably have to break it off and try again, unless I can make a somewhat flexible mounting plate that will allow for this. A combination of aluminium and rubber would probably make this possible.
Anyway, the build is on target now I've got the tricky bit (the electronics) out of the way.