I built something similar a few years ago, but using a Pi instead of an Arduino. Reading through the poster's calculations brought back memories of debugging my own orbital mechanics code at 2am while questioning all my life choices.
What impresses me most here isn't just the technical achievement, but how the project transforms abstract data into physical movement. We've become so accustomed to viewing everything through screens that there's something deeply satisfying about a physical object that silently points to a spacecraft traveling 28,000 km/h overhead with humans inside.
The mathematical transformation from TLE to actual motor positioning is non-trivial - converting between reference frames always seems straightforward on paper until you're debugging at 3am wondering why your arrow is pointing at the ground. I appreciate that they shared actual code rather than glossing over the hard parts.
For anyone wanting to build this: from my experience, the hardest part is actually the mechanical design. Getting smooth movement without backlash in consumer-grade steppers and servos takes patience. The 28BYJ-48 is a good budget choice but has noticeable "slop" in its gearing, which can make precise pointing challenging.
This reminds me of those old mechanical orreries that modeled the solar system. There's something profoundly human about building machines that help us comprehend the cosmos.
I think not a lot. An equatorial mount has the advantage that cancelling the rotation of the earth is very simple (just a constant rate rotation around one axis), so tracking inertial stars is easier, but the main movement of the ISS is due to its orbit, it’s just overlaid with the rotation of the earth. But if you have to track both axes anyways, having the rotation of the earth cancelled for free doesn’t help a lot.
I built something similar a few years ago, but using a Pi instead of an Arduino. Reading through the poster's calculations brought back memories of debugging my own orbital mechanics code at 2am while questioning all my life choices.
What impresses me most here isn't just the technical achievement, but how the project transforms abstract data into physical movement. We've become so accustomed to viewing everything through screens that there's something deeply satisfying about a physical object that silently points to a spacecraft traveling 28,000 km/h overhead with humans inside.
The mathematical transformation from TLE to actual motor positioning is non-trivial - converting between reference frames always seems straightforward on paper until you're debugging at 3am wondering why your arrow is pointing at the ground. I appreciate that they shared actual code rather than glossing over the hard parts.
For anyone wanting to build this: from my experience, the hardest part is actually the mechanical design. Getting smooth movement without backlash in consumer-grade steppers and servos takes patience. The 28BYJ-48 is a good budget choice but has noticeable "slop" in its gearing, which can make precise pointing challenging.
This reminds me of those old mechanical orreries that modeled the solar system. There's something profoundly human about building machines that help us comprehend the cosmos.
This begs for a laser pointer! Although that might not be such a great idea….
Wondering the degree to which an equatorial mount would have simplified the code (made more complex the set-up of the mount).
I think not a lot. An equatorial mount has the advantage that cancelling the rotation of the earth is very simple (just a constant rate rotation around one axis), so tracking inertial stars is easier, but the main movement of the ISS is due to its orbit, it’s just overlaid with the rotation of the earth. But if you have to track both axes anyways, having the rotation of the earth cancelled for free doesn’t help a lot.
So cool! TIL that pencil lead can be a lubricant.
Just for reference, it’s graphite. You can also get graphite powder as lubricant (for locks for example).
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