Roger,
the Starlight one (and the W/O focusers too, they are an Asian clone as far as I can tell), are simple. A hidden setscew is all that holds the knob on the shaft, and once the fine focus knob is removed, the shaft is left ready to attach the motor to. Try this
http://www.starlightinstruments.com/...Attachment.pdf it will show how their system fits.
Gary