mcp-stargazing

import json import argparse import numpy as np import astropy.units as u from astropy.coordinates import SkyCoord, get_constellation def compute_centers(step: int = 2) -> list[dict]: ra_vals = np.arange(0, 360, step, dtype=float) dec_vals = np.arange(-90, 91, step, dtype=float) ra_grid, dec_grid = np.meshgrid(ra_vals, dec_vals) ra_flat = ra_grid.ravel() dec_flat = dec_grid.ravel() sc = SkyCoord(ra=ra_flat * u.deg, dec=dec_flat * u.deg, frame="icrs") names = np.array(get_constellation(sc, constellation_list='iau')) ra_rad = np.deg2rad(ra_flat) dec_rad = np.deg2rad(dec_flat) w = np.cos(dec_rad) x = np.cos(dec_rad) * np.cos(ra_rad) * w y = np.cos(dec_rad) * np.sin(ra_rad) * w z = np.sin(dec_rad) * w centers = {} for i, n in enumerate(names): if n not in centers: centers[n] = {"sx": 0.0, "sy": 0.0, "sz": 0.0} centers[n]["sx"] += x[i] centers[n]["sy"] += y[i] centers[n]["sz"] += z[i] out = [] for n, s in centers.items(): vx = s["sx"] vy = s["sy"] vz = s["sz"] norm = np.sqrt(vx * vx + vy * vy + vz * vz) if norm == 0: continue vx /= norm vy /= norm vz /= norm ra = (np.rad2deg(np.arctan2(vy, vx)) + 360.0) % 360.0 dec = np.rad2deg(np.arcsin(vz)) out.append({"name": n, "ra": float(ra), "dec": float(dec)}) out.sort(key=lambda d: d["name"]) return out def main(): p = argparse.ArgumentParser() p.add_argument("--out", default="src/data/constellation_centers.json") p.add_argument("--step", type=int, default=2) args = p.parse_args() centers = compute_centers(step=args.step) with open(args.out, "w") as f: json.dump(centers, f, ensure_ascii=False, indent=2) print(f"written {len(centers)} entries to {args.out}") if __name__ == "__main__": main()