If astronomers had any brains, they would have used an electronic
motor drive that was crystal derived.
Astronomers have a *lot* more brains than you do!
Modern scopes are mostly servo controlled with shaft encoder feedback
under computer control these days - true even for high end amateur
scopes. This allows them to automatically slew to targets, correct for
the change in apparent motion with altitude and accept autoguiders.
Industrial stepper drives were used for a while in the late 70's, but
tended to cause unwanted structural vibration even with microstepping
compared to old synchronous clock motors driven from a sine wave.
But for a very long time cheap and ubiquitous synchronous clock motors
were the way to drive telescopes. A few customers even had Rolls Royce
cut large 359 tooth gears for the main drive so that their scope would
keep almost perfect sidereal time if the mains frequency was at exactly
50Hz. They were the ones that were most miffed about the higher and
variable mains frequency at night. This included an optical telescope by
Grubb Parsons that at one time in the 1960's was at Jodrell Bank.
It was definitely a step up from the governed clockwork drives that
preceded them and were very sensitive to balance and temperature.
Regards,
Martin Brown