Pointing to the ISS in real time
I was reminiscing over some old projects and remembered that back in 2020 - during my first year at uni - I made this fun little desktop feature:
It points to the current location of the ISS - or close enough to it at least, assuming I have it sitting on my desk in the right orientation. It's constructed out of a 28BYJ-48 stepper motor, an Arduino, and is controlled by some janky python code. You'll notice that it suddenly pulls a 180° turn; that's just to stop the wires getting tangled.
The altitude and azimuth are derived from the two line element set (TLE) moment by moment. It's not a continuous lookup. Rather, the TLE is read in once at the start of the script and all future positions are extrapolated from that. As I understand it, the ISS adjusts its course/altitude every now and then so the TLE will need to be re-sourced and loaded at regular intervals to reflect these unpredictable changes. Also, being controlled open-loop like this (the Arduino is just reading position commands over serial) means it's susceptible to motor position error accrual over time.
That being said, accuracy isn't much of a concern when you're pointing to a tiny spec of a satellite whizzing along on the other side of 12,000km of earth below your feet.
This project was inspired by this YouTube video by Practical Engineering (excellent channel). Alas, my student budget didn't quite allow for a solution as kick-ass as his.