One of my long time hobbies is star gazing. Before I get too far, I’m not much of an astronomer. I can pick out a few constellations, stars and a planet or two. With the aid of my favorite astronomy program, Stellarium, I can find lots of other objects.
A long time ago, I bought a Celestron C90. It was a 3.5″ telescope/spotting scope/1000mm camera lense. I used it for all three things and had a lot of fun with it. Then came computers… I sold the C90 to purchase a ** hold on ** 5.25″ floppy disk drive for my Commodore C64 <gasp>.
Many moons have passed since then. I am very fortunate that my wife shares my enjoyment and interest in astronomy. So for our 21st anniversary, I bought an Orion XT10 Classic Dobsonian telescope. For those of you who don’t know Orion telescopes, the XT10 is a 10″ reflecting Dobsonian. The Classic part means – ‘that’s it’ – no motor drive, no computer… nuttin’ else. Swing it around and find the objects using your muscles. Now, the scope has been designed quite nicely and is fairly easy to move around. The scope body separates from the base making it portable – one person can carry the two pieces and set things up.
I thought, mistakenly, that I could purchase a motor drive and computer for it later, but that was not to be. The base and mount on this model cannot accommodate the necessary mechanics and electronics that the manufacturer makes. Not to be deterred, I began brainstorming on how I could home-brew the necessary parts to make things work anyway.
Ideas came and went. I saw lots of projects others had put together and I finally came to the conclusion that I would need to design my solution from scratch. Phase 1 is electronic display of elevation and azimuth. Accuracy must be to at least 0.1 degrees. Phase 2 is motorized control of the telescope. An optional, but nice tie in is integration to Stellarium, so as the telescope moves, so does the display on the computer.
Like most things, ideas are a dime a dozen, and since this project has been on my brain’s back burner for quite some time, I decided not to publish anything until I had started to make some measurable progress.
As of this writing, I have been able to make good progress with Phase 1 – the electronic display of elevation and azimuth. The heart of the project is the Raspberry Pi computer. I have successfully written Python based code that talks to a precision rotary position sensor (AMS5048B) – accurate measurement down to 1/45th of a degree. In transit is an OLED for display of the data and by the end of this week (certainly before the beginning of April 2016), I should have the hardware brackets and mounts built to attach it to the telescope. To those that are anxious to get the code, please be patient, I will post it to this site when everything is ready. I will also supply plans for the mounts and other details, so if you are willing and able, you too can equip your Orion Classic XT10 (or smaller/bigger) Dobsonian with a computerized display.
2016-03-25: The 128X32 OLED arrived yesterday afternoon. I was able to solder on the header last night, and today started to work on the programming. The examples provided by the Adafruit team got me going really quick. Thanks for providing Python code guys! I was also able to download all kinds of fonts and check out how they looked on the display – very nice indeed! I will be taking this outside to see how things look in full sun and at night. My main goal for this particular project is to display degrees elevation and direction for the telescope. Some people are picky about white light during observation, but this display is so small, I don’t think that it will present a problem.
2016-03-29: Working model of AS5048 rotation position sensor and the SSD1306 OLED 128X32 display. Today, I completed the integration of the Raspberry Pi 3, and the two above mentioned devices. They are connected via the I2C bus. The Python code I have written is a combination of code provided by the Adafruit developers for the display and my own code to get the rotation sensor working. I am thinking of posting code and other information on GitHub, but haven’t set that up yet – perhaps by the end of the week. Essentially, the test program is command line driven Python code. It can accept three user inputs, one to zero calibrate the sensor, another to run the code to display the angle measured and finally, a kill to stop the process. The next major step will be to design a bracket that fits on the telescope and put the electronics in an enclosure so it can be easily managed outside. I will probably 3D print this one until I can make a more sturdy bracket and when I have a final working design.
The base sensor will be a bit more tricky as I will have to do some dis-assembly and rework the interconnect between the two pieces. In order for me to mount the magnet, the bottom will have to have the bolt fixed and rotate inside the top section. The base is in reverse right now, but I think it can be changed without too much trouble. This one, for me is the most important one as it will represent the azimuth reading, the elevation part is already configured correctly.
2016-04-04 I have created a GitHub page for this project. Please see the following link for pictures and code examples so far.
gitHub link HERE