sep function

double sep(double ra1, double dec1, double ra2, double dec2,)

Angular separation between two equatorial positions.

ra1, dec1, ra2, dec2 all in radians. Result in radians.

Implementation

double sep(double ra1, double dec1, double ra2, double dec2) {
  final sd1 = math.sin(dec1), cd1 = math.cos(dec1);
  final sd2 = math.sin(dec2), cd2 = math.cos(dec2);
  final cDra = math.cos(ra1 - ra2);
  return math.acos(sd1 * sd2 + cd1 * cd2 * cDra);
}