A Star Tracking Telescope Mount

[Chris] recently got his hands on an old telescope. While this small refractor with an altitude-azimuth mount is sufficient for taking a gander at big objects in our solar system, high-end telescopes can be so much cooler. Large reflecting telescopes can track the night sky for hours, and usually come with a computer interface and a GOTO button. Combine this with Stellarium, the open source sky map, and you can have an entire observatory in your back yard.

For [Chris]’ entry into the 2016 Hackaday Prize, he’s giving his old telescope an upgrade. With a Raspberry Pi, a few 3D printed adapters, and a new telescope mount to create a homebrew telescope computer.

The alt-az mount really isn’t the right tool for the astronomical job. The earth spins on a tilted axis, and if you want to hold things in the night sky still, it has to turn in two axes. An equatorial mount is much more compatible with the celestial sphere. Right now, [Chris] is looking into a German equatorial mount, a telescope that is able to track an individual star through the night sky using only a clock drive motor.

To give this telescope a brain, he’ll be using a Raspberry Pi, GPS, magnetometer, and ostensibly a real-time clock to make sure the build knows where the stars are. After that, it’s a simple matter of pointing the telescope via computer and using a Raspberry Pi camera to peer into the heavens with a very, very small image sensor.

While anyone with three or four hundred dollars could simply buy a telescope with similar features, that’s really not the point for [Chris], or for amateur astronomy. There is a long, long history of amateur astronomers building their own mirrors, lenses, and mounts. [Chris] is just continuing this very long tradition, and in the process building a great entry for the 2016 Hackaday Prize

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20 thoughts on “A Star Tracking Telescope Mount

  1. I use a piece of software called StarsPi (http://www.starspi.com/) the uses the RasPi for control of my astrophotography equipment (currently an SBIG STXL-11002M and Losmandy Titan (which emulates the LX200 protocol) and it might be something else to consider along with the setup. Another thing he might want to add is a good OAG with a guide-cam that can be used to automatically plate solve the region of sky the telescope is pointing at to automate alignment procedures (I believe Celestron does this with their StarSense camera)

  2. When I was a kid with a 3′ reflector, I was amazed that I would find the needle in a haystack with just a textbook. In the less polluted city back then, yes but without a ‘duino.

    1. It’s understandable. The role computer automation has played in astronomy has reshaped how we enjoy the hobby. Sometimes you just want to manually slew to the object and see if you can do spirals till you catch it in the corner of your eye. Of course, you’ll spend countless hours searching. Adding computer automation still adds time. You have to get alignment and play the star hop game. Once you are aligned though, it’s on. I remember hitting all the visible messier catalog in one night. My favorite was definitely the trifid. I don’t think I’d ever have found it if the telescope hadn’t shown me it.

  3. Computer driven alt-azi 2 axis mounts are so much simpler to setup. An equatorial mount requires getting the rotation axis precisely perpendicular to Earth’s axis so the telescope can track stars and other things as Earth rotates.

    1. The reason equitorial mounts are so popular is because of astrophotography. Alt-AZ mounts are only for visible observations. The object rotates in the FOV and blurs the photograph. Most people who begin with alt-AZ mounts usually upgrade to EQ mounts because they can’t get good long exposure images of galaxies and nebulae.

      1. Modern astrophotography has gone the way of digitally stacking many many short exposures rather than single long exposures. Helps remove this field rotation problem as well as improving resolution and S/N with cheap sensors.

    2. I made my own polar mount from a bunch of steel pipe. Cost me like $50 and it is rock solid. Not computer driven, but far better than an az-el mount (I can track an object with gentle nudges in one axis), and supports my home made Jaegers f/10 4″ refractor quite nicely.

  4. Sweet project. It has me thinking, is there anyone who has done a star tracker type automatic sextant? This has been done expensively like they had in Polaris missiles and SR-71s back in the pre-inertial guidance pre-GPS days when most multi crew aircraft had a navigator with an air sextant. Pretty much I am thinking a reverse of what stellarium does, scans for a few key stars or the sun, compares to a clock and spits out a location. Bonus points for bootstrapping time with lunar distance(computed from degrees of angle off of a navigational star or planet) super bonus points for also auto bootstrapping off of Jovian moon movement. I have never seen how they solved the problem, especially on a ballistic missile where I can only assume there were serious space and time-to-fix constraints. But I assume it is a problem much easier to solve now with our inexpensive hardware and software, and perhaps even something which could be handheld.

    1. I was thinking of a “thing” that used a single line CCD sensor like in scanners to “sight” a star, get it’s spectral “fingerprint” (all stars are unique) and using a compass/inclinometer to get position.
      I could never get a single line sensor sensitive enough.
      Even with an 8″ reflector I couldn’t get enough light to work with

    2. With a GPS you can get pretty accurate position data for setting your Equatorial mount. From that, depending on season, you can set your ‘scope for a fairly bright star (Sirius, Archernar, etc.).
      Any “fine tuning” you need to get the star centered in the viewfinder (and keep it there for a few hours) is basically adjusting your reference position.

  5. Reminds me of a project I did as a child. A camera film canister containing nine straws painted black, cut to half the height of the pot. Each with a small LDR pushed into the bottom. A small hole in the lid created a rudimentary pinhole camera/eye. I used it for tracking the sun and focusing a lens onto a constant point. Maybe a few reasonably high quality photo-transistors might have enough gain to work with moonlight.

    1. I remember reading in a early 70s ham radio magazine a project that took a 16×16 array of CdS cells and scanned them at video rates to display them on a monitor. It was to make a low res TV camera for aiming your moon bounce antenna at the moon.

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