lunar function

({double gamma, double jmax, double mag, double rho, double sdPartial, double sdPenumbral, double sdTotal, double sigma, int type}) lunar(double year)

Lunar eclipse nearest decimal year.

Returns eclipse type, jmax, gamma, rho, sigma, magnitude, and semidurations (total, partial, penumbral) in days.

Implementation

({
  int type,
  double jmax,
  double gamma,
  double rho,
  double sigma,
  double mag,
  double sdTotal,
  double sdPartial,
  double sdPenumbral,
})
lunar(double year) {
  final r = _g(_snap(year, 0.5), moonphase.meanFull(year), -0.4065, 0.1727);
  if (!r.eclipse) {
    return (
      type: none,
      jmax: 0,
      gamma: 0,
      rho: 0,
      sigma: 0,
      mag: 0,
      sdTotal: 0,
      sdPartial: 0,
      sdPenumbral: 0,
    );
  }
  final rho = 1.2848 + r.u;
  final sigma = 0.7403 - r.u;
  final aGamma = r.gamma.abs();
  var mag = (1.0128 - r.u - aGamma) / 0.545;
  int eclType;
  if (mag > 1) {
    eclType = total;
  } else if (mag > 0) {
    eclType = umbral;
  } else {
    mag = (1.5573 + r.u - aGamma) / 0.545;
    if (mag < 0) {
      return (
        type: none,
        jmax: r.jmax,
        gamma: r.gamma,
        rho: rho,
        sigma: sigma,
        mag: 0,
        sdTotal: 0,
        sdPartial: 0,
        sdPenumbral: 0,
      );
    }
    eclType = penumbral;
  }

  final p = 1.0128 - r.u;
  final t = 0.4678 - r.u;
  final n = 0.5458 + 0.04 * math.cos(r.mPrime);
  final g2 = r.gamma * r.gamma;
  final sdTotal = eclType == total ? math.sqrt(t * t - g2) / n / 24 : 0.0;
  final sdPartial = (eclType == total || eclType == umbral)
      ? math.sqrt(p * p - g2) / n / 24
      : 0.0;
  final h = 1.5573 + r.u;
  final sdPenumbral = math.sqrt(h * h - g2) / n / 24;

  return (
    type: eclType,
    jmax: r.jmax,
    gamma: r.gamma,
    rho: rho,
    sigma: sigma,
    mag: mag,
    sdTotal: sdTotal,
    sdPartial: sdPartial,
    sdPenumbral: sdPenumbral,
  );
}