Stars appear to stand still, but wait a few minutes and they won’t be in quite the same place. This means that if you want to take a long-exposure image of the sky with your DSLR you’ll have to either embrace the streaks, or use tracking hardware to compensate for this movement. Naturally, this specialized equipment can be quite expensive, but a seen here, you can now make your own 3D-printed OpenAstroTracker controlled by an Arduino Uno.
The device features a 16×2 LED display/keypad shield, along with an optional Bluetooth module for interface. When set up, it slowly rotates the camera to compensate for star movements via two steppers on a gimbal assembly.
Print files for the OpenAstroTracker are available on Thingiverse and code can be found on GitHub if you’d like to examine the design or even build your own. Its creator also plans to sell it as a DIY kit — and you can sign up to be notified when it’s available.