View Full Version here: : Diy motor drive

19-06-2016, 02:18 PM
Hi Guys,

I am new to this forum so hopefully thic topis has not been beaten to death.

I own a Saxon telescope on what i believe to be an EQ3 mount but am uncertain, my first question is how can i tell if it is an eq3?

My next question may be trickier to answer, I would like to know if anyone has made their own motor drive for this mount. I imagine the hardest part is geting the gearing right so if anyone knows how I can go qbout this it would be much appreciated If you could share your knowledge :):)

19-06-2016, 02:45 PM
Hi Fraser,

How do you know its an EQ3? Hard to tell without a photo but my EQ3 has a 20mm thick counterweight bar. I think the EQ5 has an 18mm shaft.

Motor drives can be bought, the cheapest is RA only.


You could of course do a DIY thing.

Photo is my EQ3 which is also a Saxon brand, made by Synta, with my f5 4" refractor. Great lightweight mounts these, I use mine a lot.


20-06-2016, 09:40 PM
I agree with Matt. Unless you want to make a motor and controller for fun, buying one for a mass produced mount like the EQ3 is the most practical and reasonably cheap option.

Different mount types have worms with differing numbers of teeth on the worm. You must buy exactly the right drive for the number of worm wheel teeth. You can pull the housing apart to count the worm teeth. An easier way that you can count the number of teeth by manually indexing the stationary and rotating sections of the RA then turning the worm and counting. Put a piece of electricians tape across the rotating and non-rotating sections then cut it with a sharp knife. You might need to make 120 turns to count it out. When the edges of the tape line up again, you have the gear ratio.

This page has the number of teeth on different mounts.
After you count your gear ratio, you'll be able to ID it and order the correct drive.

You don't need to worry about the dec ratio if you are just putting motors and not a GOTO controller but confirm that you have an EQ3 120 tooth worm before buying a drive.

Alternatively, bring the mount to a local store and they can probably ID it for you and sell you the drive.