Improvised Clock Drive Project

UPDATE (February 2016): I have recently built an Arduino-based stepper motor controller. For inquiries, kindly leave a comment below or send an email to eteny@nightskyinfocus.com

Most entry-level telescopes with equatorial mount do not have a built-in clock drive. Due to the absence of a tracking mechanism, these telescopes cannot be used for deep-sky photography. Taking images of galaxies, nebula, and globular clusters as well as faint objects like comets may require exposure time ranging from a few seconds to a few minutes. Without tracking, it is simply impossible to take photos of even the brightest deep-sky objects.

To address this problem, most amateur astronomers tend to improvise by constructing home-built clock drives (or motor drives). One example of such device is shown below: a clock drive made from parts of an old dot-matrix printer, a gearbox from a geared dynamo, a few fabricated metal parts, and a circuit diagram to control the motor.

Improvised motor drive (left) and its hand controller (right)

The clock drive shown can be attached to any equatorial mount through the RA fine adjustment knob. It is driven by a stepper motor, a kind of motor found in electronic devices that require precise motion control such as hard drives, scanners, and printers. The stepper is controlled by a microcontroller, a circuit that tells the number of the turns it should make every minute (revolutions per minute or RPM) and the direction of its rotation (clockwise or counterclockwise). The schematic diagram was based primarily on the original works of Mr. Rob Paisley. In order to adapt the circuit to the requirements of my telescope, I removed the unused parts of the circuit and added a number of components as well.

If more precise tracking is required, the whole setup can be connected to a computer through the parallel port and an interface can also be constructed to equip the tracker with autoguiding capabilities using an autoguider software like GuideDog and Guidemaster (note that an autoguider setup would require additional equipment like guidescope, web camera, and a computer).

The gearbox (left), stepper motor (upper right), and microcontroller circuit (lower right)

During the clock drive’s initial testing, a relatively bright deep-sky object was chosen, M42, or the Great Orion Nebula. To capture M42 using a 6-inch telescope, it must be tracked for at least 60 seconds. The mount must be perfectly leveled and polar-aligned, and most importantly, the telescope’s clock drive must be calibrated to match the rate of the Earth’s rotation. The image below shows the result of the initial testing. Tracking is unguided.

An improvised clock drive was used to produce this first-light image of the Great Orion Nebula. Tracking is unguided.
gallery_orionnebulam42_1200_832_60min_iso400
Here’s a more recent image of the Orion Nebula (November 2012), taken with a different mount and a different telescope, but still using the same stepper motor controller. Imaged with a  4-inch f/9 refractor and a Kenko NES mount.  Tracking is guided.

A similar clock drive can be built in a few days, with all parts obtained and fabricated locally. The setup can also be adapted for barn-door trackers and equatorial platforms. For queries regarding the project, please leave a comment. Clear skies!

Related page: DIY Astronomy Equipment

For tutorials on how to get started with astrophotography, click here.
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© Anthony Urbano (Manila, Philippines)


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19 thoughts on “Improvised Clock Drive Project

  1. Hi Sir!
    I was checking out your website and I found the page for the clock drive for equatorial mounts. You have stated that the drive can be adapted to barndoor mounts. May I ask how?
    I currently have a manual-driven barndoor mount, which I use to take pictures of stars and some DSOs. I have been wanting to motorize the setup, but I don’t know how… hope that you can help me with this…
    Also, I’m interested in the afocal adapter for cameras… Can I use a DSLR with that afocal adapter?
    Any response to this would be much appreciated. Thanks!

    • Hi Oliver,

      I have received the picture of your barn door tracker. Yes It can be easily adapted. I can also extend my help and volunteer some of my time for your project.

      I will send you the schematics for the Variable Speed Stepper Motor Controller during the weekend. Hopefully you would be able to find a suitable gearbox. I have much confidence that it will definitely work with your setup. I’d like to feature some of your photos once the motorized mount is finished :)

      And regarding the adapter, yes, the Universal Camera Adapter may be used to connect a DSLR to a telescope. This setup should be adequate enough for afocal imaging.

      Thanks!

      Eteny

      • Sir,

        Thanks much for responding to this inquiry. I’d really appreciate it if someone can help me out with the stepper motor drive, but I’m not really adept with electronics…I will feature some of the photos once it is finished…

  2. @Hi Eteny,
    Just found your site! Have got myself a gem1 mount which I believe is the same as the kenko. I am looking to build the drive for it……. In the process of stripping an Epson printer but if you still have the schematic for the controller it would be most helpful!
    Regards
    Trevor

  3. Hi – I recently bought a used 4.5″ f/7 reflector, it came with the standard clock drive that comes with skywatchers. It was a bit rusty, so I opened up the controller to check it out, but it was so corroded that some of the components fell out, and were too rusty to identify. (I checked that it worked when I got it, and it was OK, but the power connector had broken) as a result I have the stepper motor and cables, but no controlller. I’m interested in your DIY drive, I wonder if you could send me your wiring diagram? I might be able to modify it to run my stepper. (I have some electronics experience, but very much an amateur) Thanks.

  4. hi, i have a 5.5 inch reflector with an eq4 mount. i would really like to work on a clock drive for my mount. can you please mail me the schematic diagram for it and the list of parts? thank you vey much.

  5. Hello Eteny,
    Thank you for all of your great work with posting and sharing your projects. It has only been a dream to be able to control my telescope with stepper motors. With your help I can now see this can be a dream come true. I too, would benefit greatly (on a personal level) from your simplified schematics of where to put in potentiometers for variable speed control and switches for manual control.

      • Would it be possible to email me a more simplified schematic? I’m not very good at electrical engineering. I have put together various projects together just from schematics. I’m probably never going to be able afford commercial equipment and DIY is always first for me, there is so much more appreciation for things. Im looking to place the stepper motors on a forty year old German equatorial mount with an 8 inch reflector. I salvaged the mount from someones curbside garbage, polished the worm gears and regreased, everything worked great. The 8 inch reflecting telescope was handed down to me by a close friend when he got a new one. The tripod I made myself out of steel square tubing and piping, it weighs in at almost a hundred pounds. How big of a stepper have you used? And what type did you end up with, a unipolar or bipolar? Your schematic will get me getting to seeing the light at end of the tunnel!

      • Hi Keith, I have sent you an email. Note that you will also need some sort of a gearbox in connecting the stepper to the mount. Without it, there may not be enough torque to move the mount, and also suffer from tracking inaccuracy which may lead to having elongated stars. A small stepper will do (mine is only about the size of a roll of newly-bought electrical tape, and easily fits in the palm of my hand). A telescope that is well-balanced will only need a small motor. :)

        For ease of use, I recommend using unipolar steppers. Good luck!

  6. Hi Mr Eteny, nice and good job, Anyway, I am interested to do it myself, but totally I have no idea at this moment. Can you please send me a diagrams or details (how to do it)? Fyi, I have NES mount. Thank you so much. Have a nice day.

  7. Hi Eteny,

    Your article is very informative and interesting. May I ask how you acquired a suitable gearbox? I think I will try and use an Arduino to control the stepper.

    Thanks!

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