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Homebrew electric focuser.

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  • k3hx@juno.com
    I d be grateful for advice about making an electric focuser. I am leaning towards a 12VDC gearmotor and 3/8 timing belt drive. Have a venerable small lathe,
    Message 1 of 3 , Mar 1, 2013
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      I'd be grateful for advice about making an electric focuser. I am leaning towards a 12VDC gearmotor and 3/8" timing belt drive.

      Have a venerable small lathe, drill press, decent tooling and
      measuring devices and some machine trades skill.

      My thoughts are to enlarge the hole on a timing belt pulley and
      set-screw it to the current focusing knob and use the focuser
      mounting screws to mount a bracket for the gear motor. I've
      looked at the setups on YouTube.

      Need an honest merchant where I can get the timing belt pulleys and belt at a rational price. I do not deal with eBay.

      Also considering a "memory" function to account for the different focusing requirements of various eyepieces. Was thinking of an optical encoder that would cause a small computer (such as Raspberry Pi) to remember where it needed to be for focusing.
      For example, with a 24mm eyepiece, I'd enter "24" and the computer would tell the motor which way to turn and how far, getting feedback from the optical encoder. If I wanted to use
      a 10mm eyepiece, I'd enter "10" and the computer would again
      issue instructions to the motor. I'd need a way to "train" the
      computer as well.
      I want to avoid having a laptop computer out with the telescope.

      Be Well,

      Tim Colbert K3HX

      PS I invite you to visit our astronomy club's website:
      www.3ap.org
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    • Tom King
      Hi Tim, I am finishing up a CNC conversation for a small milling machine and also needed timing belts and pulleys. I found that MSC (www.mscdirect.com) had the
      Message 2 of 3 , Mar 2, 2013
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        Hi Tim,

        I am finishing up a CNC conversation for a small milling machine and also needed timing belts and pulleys. I found that MSC (www.mscdirect.com) had the selection for what I needed. Perhaps someone will know of a less expensive source, but at least you should be able to get the parts you need at MSC, and you might also compare prices with www.mcmaster.com, another supplier I use regularly.

        I built a focuser project a couple of years ago using a stepper motor drive. No one ever made a quality electronic focuser for my AT80ED 80mm APO refractor, so I built a USB remote controlled focuser for it with 1/3600th of a degree step control resolution, a tad better than my fingers can achieve. Some details on my modest attempt are posted here for my precision focuser:

        https://picasaweb.google.com/112161231014949540947/WSOPrecisionUSBFocuser

        Even a simpler stepper drive can work well. This is a video of the initial concept I started with, a simpler stepper driving the AT80ED's focuser:

        http://www.wataugaskies.net/equipment/wsofocus/wsofocus.php

        Good luck & '73!

        Tom King - KD5HM
        Watauga Skies Observatory
        http://www.wataugaskies.net




        "Simplicity is the ultimate sophistication." -Leonardo da Vinci-



        On Mar 1, 2013, at 12:36 PM, "k3hx@..." <k3hx@...> wrote:

        > I'd be grateful for advice about making an electric focuser. I am leaning towards a 12VDC gearmotor and 3/8" timing belt drive.
        >
        > Have a venerable small lathe, drill press, decent tooling and
        > measuring devices and some machine trades skill.
        >
        > My thoughts are to enlarge the hole on a timing belt pulley and
        > set-screw it to the current focusing knob and use the focuser
        > mounting screws to mount a bracket for the gear motor. I've
        > looked at the setups on YouTube.
        >
        > Need an honest merchant where I can get the timing belt pulleys and belt at a rational price. I do not deal with eBay.
        >
        > Also considering a "memory" function to account for the different focusing requirements of various eyepieces. Was thinking of an optical encoder that would cause a small computer (such as Raspberry Pi) to remember where it needed to be for focusing.
        > For example, with a 24mm eyepiece, I'd enter "24" and the computer would tell the motor which way to turn and how far, getting feedback from the optical encoder. If I wanted to use
        > a 10mm eyepiece, I'd enter "10" and the computer would again
        > issue instructions to the motor. I'd need a way to "train" the
        > computer as well.
        > I want to avoid having a laptop computer out with the telescope.
        >
        > Be Well,
        >
        > Tim Colbert K3HX
        >
        > PS I invite you to visit our astronomy club's website:
        > www.3ap.org




        [Non-text portions of this message have been removed]
      • Simon Morgan
        Congratulations, this is a quality piece of work. Obviously a highly skilled engineer. Simon Morgan From: lx90@yahoogroups.com [mailto:lx90@yahoogroups.com] On
        Message 3 of 3 , Mar 2, 2013
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          Congratulations, this is a quality piece of work. Obviously a highly skilled
          engineer.

          Simon Morgan



          From: lx90@yahoogroups.com [mailto:lx90@yahoogroups.com] On Behalf Of Tom
          King
          Sent: 02 March 2013 19:53
          To: lx90@yahoogroups.com
          Subject: Re: [lx90] Homebrew electric focuser.





          Hi Tim,

          I am finishing up a CNC conversation for a small milling machine and also
          needed timing belts and pulleys. I found that MSC (www.mscdirect.com) had
          the selection for what I needed. Perhaps someone will know of a less
          expensive source, but at least you should be able to get the parts you need
          at MSC, and you might also compare prices with www.mcmaster.com, another
          supplier I use regularly.

          I built a focuser project a couple of years ago using a stepper motor drive.
          No one ever made a quality electronic focuser for my AT80ED 80mm APO
          refractor, so I built a USB remote controlled focuser for it with 1/3600th
          of a degree step control resolution, a tad better than my fingers can
          achieve. Some details on my modest attempt are posted here for my precision
          focuser:

          https://picasaweb.google.com/112161231014949540947/WSOPrecisionUSBFocuser

          Even a simpler stepper drive can work well. This is a video of the initial
          concept I started with, a simpler stepper driving the AT80ED's focuser:

          http://www.wataugaskies.net/equipment/wsofocus/wsofocus.php

          Good luck & '73!

          Tom King - KD5HM
          Watauga Skies Observatory
          http://www.wataugaskies.net

          "Simplicity is the ultimate sophistication." -Leonardo da Vinci-

          On Mar 1, 2013, at 12:36 PM, "k3hx@... <mailto:k3hx%40juno.com> "
          k3hx@... <mailto:k3hx%40juno.com> > wrote:

          > I'd be grateful for advice about making an electric focuser. I am leaning
          towards a 12VDC gearmotor and 3/8" timing belt drive.
          >
          > Have a venerable small lathe, drill press, decent tooling and
          > measuring devices and some machine trades skill.
          >
          > My thoughts are to enlarge the hole on a timing belt pulley and
          > set-screw it to the current focusing knob and use the focuser
          > mounting screws to mount a bracket for the gear motor. I've
          > looked at the setups on YouTube.
          >
          > Need an honest merchant where I can get the timing belt pulleys and belt
          at a rational price. I do not deal with eBay.
          >
          > Also considering a "memory" function to account for the different focusing
          requirements of various eyepieces. Was thinking of an optical encoder that
          would cause a small computer (such as Raspberry Pi) to remember where it
          needed to be for focusing.
          > For example, with a 24mm eyepiece, I'd enter "24" and the computer would
          tell the motor which way to turn and how far, getting feedback from the
          optical encoder. If I wanted to use
          > a 10mm eyepiece, I'd enter "10" and the computer would again
          > issue instructions to the motor. I'd need a way to "train" the
          > computer as well.
          > I want to avoid having a laptop computer out with the telescope.
          >
          > Be Well,
          >
          > Tim Colbert K3HX
          >
          > PS I invite you to visit our astronomy club's website:
          > www.3ap.org

          [Non-text portions of this message have been removed]





          [Non-text portions of this message have been removed]
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