Today I installed a motorised focuser on my Newtonian. There was only one problem with it, the motor speed controller I was using does not supply enough current to the motor at low speeds so I am in the process of making a new circuit which should be much better. It works off 12v and draws next to nothing while in motion. I had a chance to try it out tonight and initial experiments show this will work very well. Hardly a sound from it too.
Anyway you can see by the picture below it is basically a Worm and Worm wheel set (out of a video recorder ejection assembly) with an adapter which was kindly turned up by the lathe operator at work. Attached directly to the focus knob and the assembly is bolted by one bolt to the telescope tube.
I have actually had this idea for quite sometime just never really installed it properly on the scope. Makes a hell of a difference with fine focusing, can only get better from now.
Andrew, watch your fingers/tie in the gears tho!
Did you see my 'belt' (O ring), driven unit? Just used an old servo (Radio control), & pulley to drive the left knob. Runs off 2 x AA batterys & is speed adjustable.
You'll find the t'scope won't move now, while getting the focus just right. Nice work. L.
I was going to use an old stepper motor (got pleanty laying around here) but could not find a suitable control circuit. Maybe I wasn't looking hard enough. I plan to add a switch for slow and micro slow movement after I get the new circuit.
Mike, If your focuser is the slightest bit 'sticky/tight' you may have to 'free' it up for the motor to drive it correctly/smoothly. Sorry, I don't have any old, 'blown/broken' servos left, (JUST FOUND ONE!). All you need is the drive unit (servo with it's innards ripped out, & a pulley wheel on the output shaft), an 'O' ring belt, a speed control with fwd&rev & a bracket to mount it on the focuser.
Regards, L.
Hi Mike, Are you getting my PM's? I have all but finished your motorized focuser. All you will have to do is make a cardboard template for the mounting bracket & bobs your uncle. Fit the servo to the alum. bracket, secure the cable & you're up & running.
I've got the JMI focusser badged as Celestron that was supplied with my version of the C8 a decade ago. I can't imaging doing without it. It makes a huge difference to critical focussing at high power when the image isn't shaking from your own touch.
yeh that's why I want one too... I wish it had a digital readout though, so I could go back to the same focal spot with the same eyepiece/ToUcam.
Laurie, will this one lock the knobs in place? ie, will you still be able to turn with your hand? I'm also wondering what will happen when I put in my coke can eyepiece..
I've just finished my stepper-motor focuser project.
Two electronic kits, a stepper motor controller and 4digit up/down counter - fitted into a jaycar box, with cables and switches. Unfortunately just the stepper motor didn't have enough torque to be reliable on it's own - so a planetary gearbox got added to the set at 1:25. This makes it 5 steps to the 0.001" focuser travel which is well below the bounds of accuracy with my R&P focuser. Mounting shown here is still in the final R&D configuration. Obviously the focus position numbers are different depending on whether you are focusing on the way "up" or "down", but this is quite reproducible and so doesn't cause much of a problem.
My original intent was to retain the ability to manually focus by turning the "motor off" and "motor on" - but with the gear box that now makes it impossible.
Mike, All I can say is that it handles my UWA 14 mm O.K. It does not "lock" at all, but there is added resistance because of the belt. You can still manually focus, as the belt just slips over the pulley.
Don't forget to make a "belt keeper", which stops you "losing it" in the grass, & we wouldn't want that now, would we? (If the belt breaks simply wind the new belt thru the open coils.) See attached.
HTH. L.
I noticed a new product called the AccuFocus on the Orion website. For only $49.95US it seems like a nice alternative. The website lists that it works with all Orion dobsonians (except the XT4.5).
That's not bad simon.. cheap too. If Loz hadn't made me one I might've gone for that.. It looks like it slips over the focus knob.. I guess it's a bit of a risk whether it will fit for non-orion dobs/focusers, but you could probably make an alternative adapter for it quite easily.
Dave, your kit looks great! Would love a digital readout on mine!
L.
