Simple motor for SkyWatcher EQ2 mount

My SkyWatcher telescope came with their entry level equatorial mount, the EQ2. This is designed to allow the right ascension axis to be motorised, so that it turns to compensate for the Earth's rotation. Without this, you must manually keep tweaking it! With the motor, you can point the telescope at something in the sky and have it "stay put" for longer. This obviously is quite important for astrophotography, but also simply for sharing a good view with anyone else. Here's how I got on with fitting the simple EQ2 motor.

There are two widely available motor kits, the economy one at about £30 with limited controls, and a multi-speed option with a controller on the end of a cable costing about £60. I opted for the cheap option - although I am already beginning to wonder if this was a false economy? The controls seem a bit fiddly for cold fingers. (Update - I did opt for the upgrade.)

The aim of this blog post is to detail installing the economy EQ2 motor, since the supplied single sheet of instructions omits a lot of details.

The box and its contents

The provided instructions

Once you realise the instruction figures are back to front, a mirror image of the actual EQ2 mount and motor, it is quite easy to mount the motor.

The instructions fail to explain how to fit the battery, or even what kind of battery. It transpires the two round unlabelled knobs on the front of the control panel are screws, and allow you take the case cover off. I could guess from the shape that a standard E-Block / 6LR61 / MN1604 / PP3 9V battery was expected, which is actually stated on some retailers' websites. It is a tight fit to squeeze it into the padded niche between the PCB and the motor:

Simple EQ2 motor with case off

With 9V battery fitted

Once the battery is fitted, you can test it works before mounting it. Flicking the power switch on you should hear the motor whining, twiddle the speed adjustment or toggle direction (the North/South switch) and the pitch changes. If you look carefully at the black rubbery drive attachment it should be turning, but very slowly. So slowly in fact that for a while I wondered if mine might be broken - but after all, the Earth only spins 15 degrees an hour.

As the minimal instructions explain, you must remove the RA control cable, exposing the shaft, and undo the nearby screw with the allen key provided - both highlighted in red in the photo below. Then the motor's black rubbery drive attachment goes onto the shaft, while the screw threads through the metal bracket.

Screw and shaft for mounting the motor

EQ2 motor mounted

Here is the view from underneath, showing the motor's black rubbery drive attachment connected to the worm gear shaft that controls the ascension - you'll want a flat head screwdriver to tighten the set screw (or relax it if you need to disengage the motor, for example if you have a flat battery).

Drive coupling, set screw marked in red

Motor on. The labels are now upside down, sloppy!

All installed and apparently working - all I need now is an evening with clear sky to test it out, get used to the new controls. Big thanks to the friendly folk at AstronomyForum.net for helping me out.

Post testing conclusions

Good thing I stayed up late tonight, the cloud cleared up and I could try tracking the moon. Jupiter wasn't out tonight (which I've previously admired pre-motor), but I was able to find Mars (or at least, a little red dot in about the right place), and then Saturn (after relocating to avoid a tree). I can't have had my polar alignment quite right, but the motorised ascension still helped. Saturn's rings looked pretty good to my novice eyes - and was worth the cold toes!

Getting the find motor control speed just right takes some fiddling, but it makes the telescope so much easier to use at high magnification. It also means you can line up a nice view, hand over to someone else for a look, and expect the object to still be there when they're done. More importantly perhaps, it makes longer exposure photography possible.

Since the RA control rod has been replaced, for fine ascension control you can use the economy motor's fine speed control. However, once you've got the motor speed just right for sidereal tracking (or tracking the moon or a planet), you don't really want to change it, so this single speed motor isn't ideal. Turning the motor off, or flicking the North/South toggle lets you go forward quickly with respect to the Earth's rotation - but there is not really a satisfactory way to move against the rotation.

For large ascension control, just loosen the control circled below which disengages the worm thread used by the motor (or the RA control rod). Apparently this is called the RA clutch (there is a matching one further up for the Dec control). Maybe my scope isn't balanced quite right, but I found trying to make small adjustments this way very tricky.

Loosen this EQ2 knob (or clutch) for free RA control

If you are willing to live with the fine RA control limitations, these single speed motors are still a very useful upgrade to the basic SkyWatcher EQ2 mount. In fact, I suspect you could modify one with a switch toggling between the variable resistor (connected to the fine speed control), and one or two fixed resistors - turning it into a simple multi-speed motor.

However, really missing the fine RA control, I decided upgrade to the more expensive multi-speed EQ-2 motor kit after all.