I started a few months ago with electronics to build a DIY star tracking mount. I learned a lot, bought a bunch of tools and boards, etc, burned a whole bunch of them by accidentally connecting the wrong pin to the wrong pin and then got distracted. I am back now restarting my project and want to share it with anyone who might be interested. The project requires a lot more "learning" before it is finished.
How it works is that an Arduino Leonardo, in this case, and a Pololu A4988 and a Bipolar Stepper Motor are wired up together and through the Arduino programming the motor is supposed to turn at a very delicately calculated speed.
The radial speed of the motor is converted into a linear movement actuated by the screw that it turns and the screw in turn moves a platform (barn door) in a radial motion that is supposed to be the same speed as, and in opposite direction of, the Planet.
Here are a couple of great references that I have used:
And there is a whole lot more information online.
The attached snapshot of the wiring is the most basic. In time I will have to add switches that control the speed, direction, etc, and I am going to have to find a way to code the magical formula for converting the radial motion into linear motion and back into radial motion again.