I made one a long time ago: two planks, a hinge, two nuts, a threaded rod, and a camera mount. Operation was by turning the threaded rod 1/4 turn every time my

I made one a long time ago: two planks, a hinge, two nuts, a threaded rod, and a camera mount. Operation was by turning the threaded rod 1/4 turn every time my HP48SX beeped. :) It's actually advantageous to be manual when you're doing this at -25C on a cold winter night in Sweden. Batteries tend to not work well at all at those temperatures. (And no, you don't need a curved threaded rod, you can just calculate what the correct rate is as a function of position.)