Drive Calculator

How to use

1. Enter the motor max speed in RPM. Motor datasheets typically list this value for the motor alone, without a gearbox. This calculator expects it to be entered that way.
2. Enter each reduction as a single ratio, where 10.5 means 10.5:1. You can also enter a fraction such as 57/11. Leave a reduction blank for 1:1. Use the add and remove buttons for additional intermediate reductions.
3. Read the results on the right. The max slew speed can be shown in deg/sec or arcsec/sec using the menu next to it.
4. To check a specific axis rate, such as a tracking rate, enter it in the lower box, in arcsec/sec or deg/sec, to see the motor speed and ticks per second it needs.

About gearbox ratios. Gearboxes are often listed with a rounded ratio, but the real ratio is usually a fraction. For example, a gearbox sold as 5:1 may actually be 57:11. If you know the real tooth counts, enter them as a fraction like 57/11. The ratio in a motor's datasheet may not be accurate. That is fine for planning, but your controller configuration needs the exact ratio.

Choosing a reduction. We suggest about 10 ticks per arcsecond for photography. The best reduction is not the same for everyone, because more reduction means finer resolution but a lower max slew speed. You have to trade slew speed for resolution, so pick the balance that suits your telescope and how you use it.