Find planetary positions using NAIF SPICE Toolkit
npm install https://github.com/firien/spice.git
Install will fetch cspice toolkit from naif.jpl.nasa.gov and compile. This takes ~6 minutes on a Raspberry Pi 4. It would be nice if this were a git submodule, but cspice is not officially offered as a git repository.
Note: The npm scripts rely on a linux environment.
Afterward you need to download generic "kernels" data. These are occassionally updated, as of Feb 2021, the generic kernels are around ~110MB. There are more accurate versions available that grow to several GBs. Additional data for comets and asteroids can be downloaded there too.
wget -P data https://naif.jpl.nasa.gov/pub/naif/generic_kernels/lsk/naif0012.tls
wget -P data https://naif.jpl.nasa.gov/pub/naif/generic_kernels/spk/planets/de440.bsp
wget -P data https://naif.jpl.nasa.gov/pub/naif/generic_kernels/pck/pck00010.tpcimport spice, { azmAlt, getTarget } from 'spice';
spice.loadKernels("./data/naif0012.tls", "./data/de440.bsp", "./data/pck00010.tpc");
// moon position at Stonehedge
let coord = { lat: 51.178809, lon: -1.826216};
let time = new Date();
time.setHours(0);
time.setMinutes(0);
time.setSeconds(0);
let moon = getTarget('moon');
for (let x=0; x < 48; ++x) {
time.setHours(time.getHours() + 1);
let {ra, dec} = spice.getPosition(moon, time);
let {azm, alt} = azmAlt(ra, dec, time, coord);
console.log([time, azm, alt].join("\t"));
}