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Equipment Discussions >> ATM, Optics and DIY Forum

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UniversalMaster
professor emeritus


Reged: 11/20/08

Motor focus
      #6134497 - 10/13/13 08:40 AM

Hi!

I plan on using a geared DC motor with my Shoestring to make a motorized focuser. However, what is good gear ratio on the DC motor? I plan on attaching it in about 1:1 to the 1:10 focus knob...

Clear Skies


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Geo.
Carpal Tunnel
*****

Reged: 10/01/08

Loc: Upstate NY
Re: Motor focus new [Re: UniversalMaster]
      #6134720 - 10/13/13 10:44 AM

Well, gearheads have all kinds of ratios. Some scope drives are 1:300. So your gearhead may have a lot more effect on overall ratio than your final drive.

You also have a lot of latitude depending on your motor's efficiency. If it will run on low voltage you can play with that for speed regulation. The JMI/Celestron Dec drives had a built in pot to alter the speed.


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UniversalMaster
professor emeritus


Reged: 11/20/08

Re: Motor focus new [Re: Geo.]
      #6134955 - 10/13/13 12:56 PM

Yeah, thanks for your answer. This is for a moonlite 2" focuser. Anyone know what ratio their own DC focus motor is using?

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Raginar
Post Laureate
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Reged: 10/19/10

Loc: Rapid CIty, SD
Re: Motor focus new [Re: UniversalMaster]
      #6137006 - 10/14/13 01:23 PM

Nope. I have one lying around. You could just direct mount it

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Mert
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Reged: 08/31/05

Loc: Spain, Pamplona
Re: Motor focus new [Re: Raginar]
      #6137603 - 10/14/13 06:15 PM

I use a 2" Moonlight, but opted for a stepper motor.
A 1:4 reduction from stepper to focus knob is used and
also microstepping is used so rather fine focus control.
Should have some image around on CN but can't find it
anymore.


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obin robinson
Carpal Tunnel
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Reged: 10/25/12

Loc: League City, TX
Re: Motor focus new [Re: UniversalMaster]
      #6137665 - 10/14/13 07:00 PM

Quote:

Hi!

I plan on using a geared DC motor with my Shoestring to make a motorized focuser. However, what is good gear ratio on the DC motor? I plan on attaching it in about 1:1 to the 1:10 focus knob...

Clear Skies




I have the FCUSB as well. I just ordered this motor:


http://www.amazon.com/gp/product/B009N81ZCC/ref=oh_details_o00_s00_i00?ie=UTF...

I plan on using the FCUSB in a dedicated camera platform but that nice slow motor should work quite well. I am going to take a trip to the local hobby shop and see if I can find some gears and belts which will work for me. I figure with all the RC cars out there something should work.

obin


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UniversalMaster
professor emeritus


Reged: 11/20/08

Re: Motor focus new [Re: obin robinson]
      #6142140 - 10/17/13 12:43 AM

thank you. now i have something to look for! i might end up just getting the orion dc motor, but it has loads of backlash. these might be better?

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