1900's cast iron stand with 16cm Dall-Kirkham Cassegrain

Notice the 'string' drives - actually very flexible stainless steel braided wire. More rigid than most (too) small worm and wheel drives and with autoguiding, very smooth and stable. Does not rely on any precision engineering at all. There is no backlash as such, but the wire is held with a spring on one end just enough so that the gear drive shaft doesn't slip. Viola - built-in safety clutch.