Galileo's Finger - an Open Source Astronomy Learning Tool





Introduction: Galileo's Finger - an Open Source Astronomy Learning Tool

Explore Science Contest

Third Prize in the
Explore Science Contest

Automation Contest

Second Prize in the
Automation Contest


Given the opportunity to use one of the Intel Galileo boards, we wanted to build something that would honour Galileo's memory and pay tribute to his discoveries. What better way than to do something related to his primary focus - astronomy.

Being an avid astronomer, and loving being able to look up into the night sky and know what star or planet I'm looking at, I thought a cheap, accurate laser pointer would be perfect.

With the right idea in mind, and three weeks in which to do it, my partner and I set off coding and building.

Step 1: BOM

This is what we needed (software side included) to build our model:


• Soldering iron
• Hot glue gun
• Drill and appropriate bits
• Saw
• Pencil


• Intel Galileo (Any micro will work – you just need serial communications and 4 output pins)
• 2 x Stepper Motors (we used Nema 17s)
• 2 x Stepper motor controllers (we used Easy Driver v4.4)
• Veroboard/Breadboard
• Some headers to mount the motor controllers
• Wires for connecting
• Ball bearings (we used parts from an old printer and harddrive - see pictures)
• Elastic bands
• Solder
• Laser pointer (please be careful with this)
• AA battery pack(or anything that can provide a steady 3V - NOT the arduino)
• Wood


• Arduino IDE
• Python 3.3
• PySerial
• PyEphem
• Stellarium

Step 2: Create the Circuit Board

You can use a breadboard, veroboard, or even print a PCB if you have the time and resources. The circuit diagram is below.

  1. Connect MS1, MS2 and the GROUND (next to step) on both boards to GROUND on the ARDUINO.
  2. Connect M+ and GND (on the PWR IN) on both boards to the 12V power supply for the motor.
  3. Connect DIR on easyDriver 1 to Arduino pin 4.
  4. Connect STEP on easyDriver 1 to Arduino pin 5.
  5. Connect DIR on easyDriver 2 to Arduino pin 6.
  6. Connect STEP on easyDriver 2 to Arduino pin 7.
  7. Connect each motor to its own easyDriver, paying attention to which coil is which.

Step 3: Software

You will need to download and install the following.

  1. Arduino
  2. Python
    • (we used python 3.3)
    • pySerial - choose the one that's correct for your version of python
    • phEphem - again, watch python version you are using
  3. Stellarium

TelescopeMotorController (both arduino code and python code) - Github Source

Note: A special thanks to Sven Steinbauer (GitHub) for the python code (pyscope)

A special note here: You will need to make some changes to the python code. Specifically,

  1. The com port used (this is almost guaranteed)
  2. The city you are in (or at least your lat/long)
  3. The degrees on the stepper motor
  4. The gearing ratio

All of these are commented as to where you might need to change them

Step 4: Construction

This part is fairly simple. You just need to be able to move the laser on 2 axes. The truth is almost anything will work, and because we did not make out model from standard parts (mostly e-Waste and some cheap wood), it's hard to be specific about the build. I have attached the pictures of our model below, so you can get an idea of what to build. In short:

  • There are 5 wooden pieces
    • 2 wheels for X-axis/azimuth (we used 2 instead of 1 for accuracy.)
    • a mount for the X-axis/azimuth bearing (harddrive bearing)
    • a mount for the Y-axis/altitude bearing
    • a base to mount everything on
  • Once the wooden pieces have been made, cut out the holes to place the bearings, and fix the bearings down
  • Attach the laser to the altitude bearing. We had to remove the batteries from the laser and mount them separately in a battery clip - the bearing would not support its entire weight)
  • Stick it all together! (just make sure the parts that can move, still move!)

Step 5: Completed Product

Enjoy your low cost, open source starfinder!

2 People Made This Project!

  • Please send code-EsM1

    EsM1 made it!

  • This is great - the ...-BillRowe

    BillRowe made it!


  • Epilog Challenge 9

    Epilog Challenge 9
  • Sew Warm Contest 2018

    Sew Warm Contest 2018
  • Gluten Free Challenge

    Gluten Free Challenge

We have a be nice policy.
Please be positive and constructive.




can be used as aiming/ star tracking for telescope, yes?

Hi Dr Luthor

Yes, it can. One of the lecturers in our astronomy department uses something similar to calibrate her telescope.

can this run on a mac?

acredito que faltam detalhes sobre o telescopio... a parte mecanica logicae cnc e facil.

onde encontro dados sobre o telescópio?

This qualifies as an outdoor laser display. I HIGHLY discourage anyone from building and using this outdoors in the USA. The FAA has pulled the document(s) pertaining to outdoor laser displays from their website. They just pulled them yesterday with no explanation. You must call them and tell them when and where you will be running this in order to be granted a variance. If you are caught, we are talking thousands of dollars in fines and possibly jail or even prison time. But now that they have deleted the legal documents, I have no idea what they might do to you. The beam can be seen for miles and is like a big arrow pointing right at you, making you very easy to find. I want everyone out there to know this. We are living in a very messed up world right now.

Thank you, this is very valid. Here in SA though there's less of a restriction, which is nice. I have added a warning, thank you for your input.

I'd still love to see a picture of what it looks like with the laser operating. Mine works well enough with a simple pointer but the laser would be awesome.

Perhaps, not so messed up... if the documents were pulled. When I first read this, I had an image of looking out over the night sky and seeing amateur astronomers with galileo's Fingers pointing up at various stellar objects as if saying, night sky lovers live here, only to be replaced by an image of Uncle Sam and his finger smashing mallet crushing my blissful scene.

I then had a few thoughts; 1: Perhaps a lower strength laser, that would maybe make a slightly visible but lower powered finger, or 2: using a red-dot pointer, like those on telescopes which are small, virtual pointing devices that don't actually emit a beam, or do, but only visible as a pointing scope, and obviously legal, or 3: use a pointing stick with crosshairs that one could merely sight along to see where it's pointing.

Obviously this device was meant to 'virtually' touch the stellar object where one would see it with the naked eye, or meant to be attached to a telescope to give one the superior locating power found in more expensive telescopes. Still, with the restriction, I think it would bear an in depth examination, and possible contact with the FCC to discover the exact limitations required to be legal with such a device as we know laser pointers are used in classrooms, and as cat toys and if it was a problem pointing them into the sky, most of use would have been arrested by now. I think we'd just need a laser, that would dissipate the light such that it spread and the beam dissipated below a certain altitude.

Of course, if we're going to get paranoid, any system, no matter how little or no power existed in the finger, could be built to swap out a more efficient and powerful device for ulterior purposes. And, I would ultimately like to believe that Uncle is not out to destroy the hopes of amateur scientists, and expect that like powered experimental rockets used by kids today would not be modified and along with a finger used to target objects in the air. There comes a point where Uncle has to grant some innocence where innocence exists because, as the old saying goes, or a variant of it, "locks", or laws in this case, do not exist to keep out thieves, they're to keep innocent people innocent.

I'm sure anyone so minded could modify any of this tech to suit whatever purpose came to mind. I'd like to think that common sense is still in play here, especially with Uncle Sam. Better to state the requirements to make and use such things rather than scream "doom", and hide in corners for fear of retaliation.

No one is screaming. I am merely stating the facts to inform the less informed among us of the laws and available documents, or in this case, the lack thereof pertaining to outdoor laser displays. Until several days ago, they had been available at It was a more up to date version of

According to these laws, all outdoor lasers exceeding 5µW/cm² are banned within 10 miles of an airport. It does not specify what kind or type of airport, it just says airport. This effectively means absolutely no laser may be used outdoors, including your 5,000x more powerful cat toy. (Very generous figure, here, actually) Most people in this country live less than 10 miles from some kind of airport.
But apparently these laws are now out of date.