Thoughts on a cheap motorised focusser

[Gina]

I've been looking at various designs for motorised focusers and these generally use stepper motors. This is clearly the best way of doing it but the stepper motor control seems expensive.

I'm considering using a cheaper alternative of a small DC motor and gearing. Such as available from Maplin in the UK for £10. The control is simply a DC voltage of either polarity. One polarity for in and the other for out. The applied voltage controls the rate of movement. The electronics for this is very simple.

I have one of these motor/gearboxes plus worm gear driving my EQ2 mount. A regulated, fixed, low voltage provides tracking (sidereal motion) whilst an on-off-on momentary toggle switch applies the full 12v in either polarity. A 2 pole changeover switch chooses this or the low voltage sidereal drive. This system give me sidereal tracking or fast slewing on the RA motion.

[Merlin66]

That will work. That's basically all the SW electronic focuser is but with all the necessary attachment screws etc......and the battery box.....and the switches.