Yet another motorized focuser!

[Velikovsky]

If you find yourself like me with a Sky Watcher + EQ3-2 and one of those cheap (~100quid is only fairly cheap I suppose) Chinese dual axis motor drives, the ones with the Dec motor that can have U falling asleep while you wait for it to track 10Degs and at the same time hate the manual focuser on the Sky Watcher...then you can solve both problems in one piece of "jury rigging".

You could, of course, go buy a motorized focuser and drill up some new holes in your scope to accommodate it, but...

Here's what I did.

1: Remove the Dec motor and clutch assembly.

2: Attach the clutch assembly to the end of the focus axle using some 6mm to 8mm shaft converter. You can buy one from

Como Drills (MFACOMODRILLS.COM) but I made my own since I'm impatient, I had an afternoon, a saw, a drill and a handy piece of bar.

Danger: the mechanically inclined could lose hours and hours browsing the catalog on Como Drills!

3: On the focuser, the plate which secures the axle on the focuser is rectangular and has 4 generously long screws. A simple rectangular piece of 1mm plate bent at 90degs in the middle and cut & drilled to shape will bolt down on top of the axle plate and you get a nice simple mount plate for the motor.

4: The hole on the plate to attach the motor is pretty easy, since the location doesn't have to be that accurate. The shaft converter from stage 2 can move a little up and down the shaft to get an accurate meshing for the 2 cogs.

What turned out neat was we can loosen the clutch and manually adjust the focus so its close, then tighten the clutch, retire to the shed and use the Dec control on the dual axis remote to fine focus the scope while watching the image on the Canon Live View software.

Pretty neat, I thought, armchair astronomy.

(I do NOT advocate doing this to your telescope. Do not attempt this unless you know what you are doing. The wrong bodge can reduce your optical marvel to an irrevocable box-of-bits - you have been warned).

[BlueAstra]

Welcome to the DIY motor focus club! Good job, well executed.

[nightfisher]

very impressive, glad you posted it here

[yesyes]

Looking at the gears it looks like the focuser (smaller gear) will rotate faster than the motor (bigger gear). Is that intentional? I would have though it should be the other way around. Or are there more gears in the motor housing?

[Velikovsky]

The motor is a hugely geared down stepper motor - I said somewhere else the motor is from a dual axis eq3-2 drive, and its the Dec motor. for some reason the manufacturer thought it right to turn Dec at about the same speed as RA, which means thew gear in the motor turns slower than 1rpm, something like that. That means its slow enough to get fairly accurate (even with my eyesight!) - which will be enhanced by a Bahtinov I'm cutting out tomorrow (Thx SGL - I never heard of one before!).

I understand why the makers of cheap dual axis motor kits make the dec adjustment motor so slow - its so they can use the same motor for both axes - save money - but that makes Dec so slow you really don't want to use it.