nutationCorrection function

({double dAlpha, double dDelta}) nutationCorrection(double ra, double dec, double jd)

Returns nutation corrections for equatorial coordinates.

ra, dec in radians, jd is Julian day. Returns corrections (dAlpha, dDelta) in radians. Invalid for objects very near the celestial poles.

Implementation

({double dAlpha, double dDelta}) nutationCorrection(
    double ra, double dec, double jd) {
  final eps = nut.meanObliquity(jd);
  final sEps = math.sin(eps);
  final cEps = math.cos(eps);
  final n = nut.nutation(jd);
  final sAlpha = math.sin(ra);
  final cAlpha = math.cos(ra);
  final tDelta = math.tan(dec);
  return (
    dAlpha: (cEps + sEps * sAlpha * tDelta) * n.dPsi - cAlpha * tDelta * n.dEps,
    dDelta: sEps * cAlpha * n.dPsi + sAlpha * n.dEps,
  );
}