Celestia Forums

Err, I apologize if this is completely offtopic, but...

I'm interested in constructing a flat-projection orrery (where everything is on a single plane). The device won't be a precise representation of solar distances, and I'm dropping Pluto for simplicity, but the device should be roughly accurate for planetary positions (no moons though).

I'll be moving the planets on geared rings, so my accuracy will probably be about one percent of an orbit (ie., hideously inaccurate, but good enough for the casual observer).

So, my question: does anyone have recommendations for hardware or software? I've been thinking that I could perhaps repurpose CNC milling gear, but that's a little pricey.

Recomend you use stepper motors instead of AC or DC types as a stepper is a digital motor that wont produce angular error variations like other types. This means that you would also need a stepper driver board and some software to control speed and direction. Many electronics shops sell kits for these with suplied software.

This has a few more advantages too:
1) if all objects are driven by a small stepper, then the relative error is a fixed value, ie it won't drift with time or the number of orbits.
2) Varying the relative time scale (go forward/back and at differrent rates) is done via software.
3) It may actually be cheaper than making lots of gears and getting the ratio's correct.
4) Since it's computer controlled anyway, it can be intefaced to other programs, eg, CELESTIA
5) Mechanical hardware now consists of pipes, rods and gears of any ratio (within limits) to turn the pipes as the software can compensate for the gear ratios.



Hope that helps