nice! i started similar project too: https://observablehq.com/@igor-a1/my-orloj but have not good accuracy in sun-moon position, like swiss ephemeris. but i working on it ;)
Super nice project thanks for sharing this. To learn a bit about d3 i started adding constellation boundaries and stars (https://observablehq.com/d/9af789503385a285). Endgoal is to use the svg with a laser cutter to turn this into an actual clock.