Clip-on motor-focus

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rwilkinson
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Joined: Mon Oct 12, 2009 6:47 pm
Location: Bolton

Clip-on motor-focus

Post by rwilkinson » Sat Apr 05, 2014 8:18 am

Whilst I was practising imaging with a little 60mm achromat (see viewtopic.php?f=18&t=652 and the April edition of The Bolton Astronomer), I realised just how much I missed a motorised focus facility. This would allow fine-adjustments of the focus without touching the 'scope and then having to wait a few seconds for the vibrations to die down.

So I've just built a working prototype, using a couple of plastic gear-wheels and a 6 RPM DC motor (all bought via eBay for under a tenner):
c60imaging.jpg
Imaging with a Philips TouCam on an old Tasco 60mm achromat with clip-on focus motor
c60imaging.jpg (259.43 KiB) Viewed 6405 times
I cut out the centre of the 40mm gear, so that it becomes a "toothed ring" which fits tightly over the existing focus-knob, and the motor is attached to a home-made bracket (just a metal strip and a couple of plastic blocks) fastened to the underside of the focuser using a pair of plastic-coated sprung metal "tool-clips" (also from eBay).
The motor runs from a PP3 battery, controlled by a simple momentary-action reversing-switch (or a pair of SPDT push-buttons).
Or when I want to set up my wire-less remote-control system (see the April edition of The Bolton Astronomer), I can use electronic switches (or relays) controlled by the LPT (or USB) port of the outdoor laptop which is linked to the mount and webcam.

There will be more ideas for motorised-focus projects in the next edition of The Bolton Astronomer.

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rwilkinson
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Posts: 1345
Joined: Mon Oct 12, 2009 6:47 pm
Location: Bolton

Clip-on motor-focus for SkyMak

Post by rwilkinson » Sun May 11, 2014 3:16 pm

The Focus-Pocus project now has a solution for the SkyWatcher Maksutov optical tubes, (of which the Society has two), which simply clips onto the body of the eyepiece-holder:
skymakmotor.jpg
Prototype clip-on focus-motor on a SkyWatcher 90mm Maksutov ( BAS 171 )
skymakmotor.jpg (304.42 KiB) Viewed 6330 times
First I slid off the rubber focus-knob and sliced it in half with a craft-knife, to allow a hollowed-out plastic gear-wheel to be mounted over the spindle. Then the motor (an 80RPM 12V DC type with a miniature gearbox) was fixed to an arm bolted onto a tool-clip which grips the eyepiece-holder. The clip may be easily rotated to engage or disengage the gears, thus allowing rapid manual coarse-focus and then electric fine-focus.
The motor will run from a 9V or 6V battery via a simple centre-off reversing-switch (or a pair of SPDT push-buttons), or one of the computer-linked control boxes (see the May edition of The Bolton Astronomer).

The motor/gearbox, plastic-coated tool-clip and plastic gear-wheel all came from eBay traders (total cost less than a tenner) and the little brass worm-wheel is a Brian Webber special.

jpinna

Re: Clip-on motor-focus

Post by jpinna » Mon May 12, 2014 10:23 am

That's a excellent way to fit a motor drive to a Mak Ross. I could not work out how to fit mine onto the mak without using a big bracket, this way it looks a much tidier job.

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