Hi Clive,
I've come across direct drive mounts and motors, but don't think I can delve into them.
I have been looking at harmonic gearboxes though.
http://www.acrodyne.com.au/products/...harmonic-drive
for now, my approach is not to use worm gears, but either timing belts or friction drive if I can get the surface machined well enough and reduction ratios reasonable as I'm using 1/32 microstepping. so reasonably high torque at the last stage with relatively low overall gear reduction.
I'm using ovoid gearboxes like the ones in the losmandy mounts, and timing pulleys.
from what i've read, pec and backlash can be adjusted to within 5 arc secs and since we have limitations in viewing, that should be ample.