// David Moews, 2008-VI-14; revised 2008-VIII-2

/*
 * precess() and get_name() are adapted from program.c, from
 * ftp://cdsarc.u-strasbg.fr/pub/cats/VI/42/program.c
 * which is from
 * CDS (Centre de donnees astronomiques de Strasbourg) catalog VI/42; also see
 *
 * Identification of a constellation from a position,
 * Nancy G. Roman,
 * PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC,
 * 99 (July 1987), pp. 695-699.
 *
 * Program.c says:
 * This program is a translation with a few adaptations of the 
 * Fortran program.f, made by FO @ CDS  (francois@simbad.u-strasbg.fr)  
 * in November 1996.
 */

//
// ra1, dec1: RA, dec coordinates, in radians, for EPOCH1, where the epoch is in years AD.
// Output: [RA, dec], in radians, precessed to EPOCH2, where the epoch is in years AD.
//
// Original comment:
// Herget precession, see p. 9 of Publ. Cincinnati Obs., No. 24.
//
function precess(ra1, dec1, epoch1, epoch2)
{
  var cdr, csr;
  var x1, x2, r;
  var t, st, a, b, c, sina, sinb, sinc, cosa, cosb, cosc, ra2, dec2;

  cdr = Math.PI / 180.0;
  csr = cdr / 3600.0;
  a = Math.cos(dec1);
  x1 = [a*Math.cos(ra1), a*Math.sin(ra1), Math.sin(dec1)];
  t = 0.001*(epoch2 - epoch1);
  st = 0.001*(epoch1 - 1900.0);
  a = csr*t*(23042.53 + st*(139.75 + 0.06*st) + t*(30.23 - 0.27*st + 18.0*t));
  b = csr*t*t*(79.27 + 0.66*st + 0.32*t) + a;
  c = csr*t*(20046.85 - st*(85.33 + 0.37*st) + t*(-42.67 - 0.37*st - 41.8*t));
  sina = Math.sin(a);
  sinb = Math.sin(b);
  sinc = Math.sin(c);
  cosa = Math.cos(a);
  cosb = Math.cos(b);
  cosc = Math.cos(c);
  r = [[0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0]];
  r[0][0] = cosa*cosb*cosc - sina*sinb;
  r[0][1] = -cosa*sinb - sina*cosb*cosc;
  r[0][2] = -cosb*sinc;
  r[1][0] = sina*cosb + cosa*sinb*cosc;
  r[1][1] = cosa*cosb - sina*sinb*cosc;
  r[1][2] = -sinb*sinc;
  r[2][0] = cosa*sinc;
  r[2][1] = -sina*sinc;
  r[2][2] = cosc;
  x2 = [0.0, 0.0, 0.0];
  for (var i = 0; i < 3; i++)
      x2[i] = r[i][0]*x1[0] + r[i][1]*x1[1] + r[i][2]*x1[2];
  ra2 = Math.atan2(x2[1], x2[0]);
  if (ra2 < 0.0)
     ra2 += 2.0 * Math.PI;
  dec2 = Math.asin(x2[2]);
  return [ra2, dec2];
}


/*
 * From ftp://cdsarc.u-strasbg.fr/pub/cats/VI/42/data.dat .
 * This table gives the constellation boundaries.
 * Each constellation is bounded by lines of constant RA or constant declination,
 * in the 1875 equinox coordinate system.
 *
 * Each line of the table consists of 
 * (1) lower right ascension boundary (hours)
 * (2) upper right ascension boundary (hours)
 * (3) lower (southern) declination boundary (degrees)
 * (4) constellation abbreviation (3 letters)
 */
var table =
[
[0.0000,24.0000,88.0000,'UMi'],
[8.0000,14.5000,86.5000,'UMi'],
[21.0000,23.0000,86.1667,'UMi'],
[18.0000,21.0000,86.0000,'UMi'],
[0.0000,8.0000,85.0000,'Cep'],
[9.1667,10.6667,82.0000,'Cam'],
[0.0000,5.0000,80.0000,'Cep'],
[10.6667,14.5000,80.0000,'Cam'],
[17.5000,18.0000,80.0000,'UMi'],
[20.1667,21.0000,80.0000,'Dra'],
[0.0000,3.5083,77.0000,'Cep'],
[11.5000,13.5833,77.0000,'Cam'],
[16.5333,17.5000,75.0000,'UMi'],
[20.1667,20.6667,75.0000,'Cep'],
[7.9667,9.1667,73.5000,'Cam'],
[9.1667,11.3333,73.5000,'Dra'],
[13.0000,16.5333,70.0000,'UMi'],
[3.1000,3.4167,68.0000,'Cas'],
[20.4167,20.6667,67.0000,'Dra'],
[11.3333,12.0000,66.5000,'Dra'],
[0.0000,0.3333,66.0000,'Cep'],
[14.0000,15.6667,66.0000,'UMi'],
[23.5833,24.0000,66.0000,'Cep'],
[12.0000,13.5000,64.0000,'Dra'],
[13.5000,14.4167,63.0000,'Dra'],
[23.1667,23.5833,63.0000,'Cep'],
[6.1000,7.0000,62.0000,'Cam'],
[20.0000,20.4167,61.5000,'Dra'],
[20.5367,20.6000,60.9167,'Cep'],
[7.0000,7.9667,60.0000,'Cam'],
[7.9667,8.4167,60.0000,'UMa'],
[19.7667,20.0000,59.5000,'Dra'],
[20.0000,20.5367,59.5000,'Cep'],
[22.8667,23.1667,59.0833,'Cep'],
[0.0000,2.4333,58.5000,'Cas'],
[19.4167,19.7667,58.0000,'Dra'],
[1.7000,1.9083,57.5000,'Cas'],
[2.4333,3.1000,57.0000,'Cas'],
[3.1000,3.1667,57.0000,'Cam'],
[22.3167,22.8667,56.2500,'Cep'],
[5.0000,6.1000,56.0000,'Cam'],
[14.0333,14.4167,55.5000,'UMa'],
[14.4167,19.4167,55.5000,'Dra'],
[3.1667,3.3333,55.0000,'Cam'],
[22.1333,22.3167,55.0000,'Cep'],
[20.6000,21.9667,54.8333,'Cep'],
[0.0000,1.7000,54.0000,'Cas'],
[6.1000,6.5000,54.0000,'Lyn'],
[12.0833,13.5000,53.0000,'UMa'],
[15.2500,15.7500,53.0000,'Dra'],
[21.9667,22.1333,52.7500,'Cep'],
[3.3333,5.0000,52.5000,'Cam'],
[22.8667,23.3333,52.5000,'Cas'],
[15.7500,17.0000,51.5000,'Dra'],
[2.0417,2.5167,50.5000,'Per'],
[17.0000,18.2333,50.5000,'Dra'],
[0.0000,1.3667,50.0000,'Cas'],
[1.3667,1.6667,50.0000,'Per'],
[6.5000,6.8000,50.0000,'Lyn'],
[23.3333,24.0000,50.0000,'Cas'],
[13.5000,14.0333,48.5000,'UMa'],
[0.0000,1.1167,48.0000,'Cas'],
[23.5833,24.0000,48.0000,'Cas'],
[18.1750,18.2333,47.5000,'Her'],
[18.2333,19.0833,47.5000,'Dra'],
[19.0833,19.1667,47.5000,'Cyg'],
[1.6667,2.0417,47.0000,'Per'],
[8.4167,9.1667,47.0000,'UMa'],
[0.1667,0.8667,46.0000,'Cas'],
[12.0000,12.0833,45.0000,'UMa'],
[6.8000,7.3667,44.5000,'Lyn'],
[21.9083,21.9667,44.0000,'Cyg'],
[21.8750,21.9083,43.7500,'Cyg'],
[19.1667,19.4000,43.5000,'Cyg'],
[9.1667,10.1667,42.0000,'UMa'],
[10.1667,10.7833,40.0000,'UMa'],
[15.4333,15.7500,40.0000,'Boo'],
[15.7500,16.3333,40.0000,'Her'],
[9.2500,9.5833,39.7500,'Lyn'],
[0.0000,2.5167,36.7500,'And'],
[2.5167,2.5667,36.7500,'Per'],
[19.3583,19.4000,36.5000,'Lyr'],
[4.5000,4.6917,36.0000,'Per'],
[21.7333,21.8750,36.0000,'Cyg'],
[21.8750,22.0000,36.0000,'Lac'],
[6.5333,7.3667,35.5000,'Aur'],
[7.3667,7.7500,35.5000,'Lyn'],
[0.0000,2.0000,35.0000,'And'],
[22.0000,22.8167,35.0000,'Lac'],
[22.8167,22.8667,34.5000,'Lac'],
[22.8667,23.5000,34.5000,'And'],
[2.5667,2.7167,34.0000,'Per'],
[10.7833,11.0000,34.0000,'UMa'],
[12.0000,12.3333,34.0000,'CVn'],
[7.7500,9.2500,33.5000,'Lyn'],
[9.2500,9.8833,33.5000,'LMi'],
[0.7167,1.4083,33.0000,'And'],
[15.1833,15.4333,33.0000,'Boo'],
[23.5000,23.7500,32.0833,'And'],
[12.3333,13.2500,32.0000,'CVn'],
[23.7500,24.0000,31.3333,'And'],
[13.9583,14.0333,30.7500,'CVn'],
[2.4167,2.7167,30.6667,'Tri'],
[2.7167,4.5000,30.6667,'Per'],
[4.5000,4.7500,30.0000,'Aur'],
[18.1750,19.3583,30.0000,'Lyr'],
[11.0000,12.0000,29.0000,'UMa'],
[19.6667,20.9167,29.0000,'Cyg'],
[4.7500,5.8833,28.5000,'Aur'],
[9.8833,10.5000,28.5000,'LMi'],
[13.2500,13.9583,28.5000,'CVn'],
[0.0000,0.0667,28.0000,'And'],
[1.4083,1.6667,28.0000,'Tri'],
[5.8833,6.5333,28.0000,'Aur'],
[7.8833,8.0000,28.0000,'Gem'],
[20.9167,21.7333,28.0000,'Cyg'],
[19.2583,19.6667,27.5000,'Cyg'],
[1.9167,2.4167,27.2500,'Tri'],
[16.1667,16.3333,27.0000,'CrB'],
[15.0833,15.1833,26.0000,'Boo'],
[15.1833,16.1667,26.0000,'CrB'],
[18.3667,18.8667,26.0000,'Lyr'],
[10.7500,11.0000,25.5000,'LMi'],
[18.8667,19.2583,25.5000,'Lyr'],
[1.6667,1.9167,25.0000,'Tri'],
[0.7167,0.8500,23.7500,'Psc'],
[10.5000,10.7500,23.5000,'LMi'],
[21.2500,21.4167,23.5000,'Vul'],
[5.7000,5.8833,22.8333,'Tau'],
[0.0667,0.1417,22.0000,'And'],
[15.9167,16.0333,22.0000,'Ser'],
[5.8833,6.2167,21.5000,'Gem'],
[19.8333,20.2500,21.2500,'Vul'],
[18.8667,19.2500,21.0833,'Vul'],
[0.1417,0.8500,21.0000,'And'],
[20.2500,20.5667,20.5000,'Vul'],
[7.8083,7.8833,20.0000,'Gem'],
[20.5667,21.2500,19.5000,'Vul'],
[19.2500,19.8333,19.1667,'Vul'],
[3.2833,3.3667,19.0000,'Ari'],
[18.8667,19.0000,18.5000,'Sge'],
[5.7000,5.7667,18.0000,'Ori'],
[6.2167,6.3083,17.5000,'Gem'],
[19.0000,19.8333,16.1667,'Sge'],
[4.9667,5.3333,16.0000,'Tau'],
[15.9167,16.0833,16.0000,'Her'],
[19.8333,20.2500,15.7500,'Sge'],
[4.6167,4.9667,15.5000,'Tau'],
[5.3333,5.6000,15.5000,'Tau'],
[12.8333,13.5000,15.0000,'Com'],
[17.2500,18.2500,14.3333,'Her'],
[11.8667,12.8333,14.0000,'Com'],
[7.5000,7.8083,13.5000,'Gem'],
[16.7500,17.2500,12.8333,'Her'],
[0.0000,0.1417,12.5000,'Peg'],
[5.6000,5.7667,12.5000,'Tau'],
[7.0000,7.5000,12.5000,'Gem'],
[21.1167,21.3333,12.5000,'Peg'],
[6.3083,6.9333,12.0000,'Gem'],
[18.2500,18.8667,12.0000,'Her'],
[20.8750,21.0500,11.8333,'Del'],
[21.0500,21.1167,11.8333,'Peg'],
[11.5167,11.8667,11.0000,'Leo'],
[6.2417,6.3083,10.0000,'Ori'],
[6.9333,7.0000,10.0000,'Gem'],
[7.8083,7.9250,10.0000,'Cnc'],
[23.8333,24.0000,10.0000,'Peg'],
[1.6667,3.2833,9.9167,'Ari'],
[20.1417,20.3000,8.5000,'Del'],
[13.5000,15.0833,8.0000,'Boo'],
[22.7500,23.8333,7.5000,'Peg'],
[7.9250,9.2500,7.0000,'Cnc'],
[9.2500,10.7500,7.0000,'Leo'],
[18.2500,18.6622,6.2500,'Oph'],
[18.6622,18.8667,6.2500,'Aql'],
[20.8333,20.8750,6.0000,'Del'],
[7.0000,7.0167,5.5000,'CMi'],
[18.2500,18.4250,4.5000,'Ser'],
[16.0833,16.7500,4.0000,'Her'],
[18.2500,18.4250,3.0000,'Oph'],
[21.4667,21.6667,2.7500,'Peg'],
[0.0000,2.0000,2.0000,'Psc'],
[18.5833,18.8667,2.0000,'Ser'],
[20.3000,20.8333,2.0000,'Del'],
[20.8333,21.3333,2.0000,'Equ'],
[21.3333,21.4667,2.0000,'Peg'],
[22.0000,22.7500,2.0000,'Peg'],
[21.6667,22.0000,1.7500,'Peg'],
[7.0167,7.2000,1.5000,'CMi'],
[3.5833,4.6167,0.0000,'Tau'],
[4.6167,4.6667,0.0000,'Ori'],
[7.2000,8.0833,0.0000,'CMi'],
[14.6667,15.0833,0.0000,'Vir'],
[17.8333,18.2500,0.0000,'Oph'],
[2.6500,3.2833,-1.7500,'Cet'],
[3.2833,3.5833,-1.7500,'Tau'],
[15.0833,16.2667,-3.2500,'Ser'],
[4.6667,5.0833,-4.0000,'Ori'],
[5.8333,6.2417,-4.0000,'Ori'],
[17.8333,17.9667,-4.0000,'Ser'],
[18.2500,18.5833,-4.0000,'Ser'],
[18.5833,18.8667,-4.0000,'Aql'],
[22.7500,23.8333,-4.0000,'Psc'],
[10.7500,11.5167,-6.0000,'Leo'],
[11.5167,11.8333,-6.0000,'Vir'],
[0.0000,0.3333,-7.0000,'Psc'],
[23.8333,24.0000,-7.0000,'Psc'],
[14.2500,14.6667,-8.0000,'Vir'],
[15.9167,16.2667,-8.0000,'Oph'],
[20.0000,20.5333,-9.0000,'Aql'],
[21.3333,21.8667,-9.0000,'Aqr'],
[17.1667,17.9667,-10.0000,'Oph'],
[5.8333,8.0833,-11.0000,'Mon'],
[4.9167,5.0833,-11.0000,'Eri'],
[5.0833,5.8333,-11.0000,'Ori'],
[8.0833,8.3667,-11.0000,'Hya'],
[9.5833,10.7500,-11.0000,'Sex'],
[11.8333,12.8333,-11.0000,'Vir'],
[17.5833,17.6667,-11.6667,'Oph'],
[18.8667,20.0000,-12.0333,'Aql'],
[4.8333,4.9167,-14.5000,'Eri'],
[20.5333,21.3333,-15.0000,'Aqr'],
[17.1667,18.2500,-16.0000,'Ser'],
[18.2500,18.8667,-16.0000,'Sct'],
[8.3667,8.5833,-17.0000,'Hya'],
[16.2667,16.3750,-18.2500,'Oph'],
[8.5833,9.0833,-19.0000,'Hya'],
[10.7500,10.8333,-19.0000,'Crt'],
[16.2667,16.3750,-19.2500,'Sco'],
[15.6667,15.9167,-20.0000,'Lib'],
[12.5833,12.8333,-22.0000,'Crv'],
[12.8333,14.2500,-22.0000,'Vir'],
[9.0833,9.7500,-24.0000,'Hya'],
[1.6667,2.6500,-24.3833,'Cet'],
[2.6500,3.7500,-24.3833,'Eri'],
[10.8333,11.8333,-24.5000,'Crt'],
[11.8333,12.5833,-24.5000,'Crv'],
[14.2500,14.9167,-24.5000,'Lib'],
[16.2667,16.7500,-24.5833,'Oph'],
[0.0000,1.6667,-25.5000,'Cet'],
[21.3333,21.8667,-25.5000,'Cap'],
[21.8667,23.8333,-25.5000,'Aqr'],
[23.8333,24.0000,-25.5000,'Cet'],
[9.7500,10.2500,-26.5000,'Hya'],
[4.7000,4.8333,-27.2500,'Eri'],
[4.8333,6.1167,-27.2500,'Lep'],
[20.0000,21.3333,-28.0000,'Cap'],
[10.2500,10.5833,-29.1667,'Hya'],
[12.5833,14.9167,-29.5000,'Hya'],
[14.9167,15.6667,-29.5000,'Lib'],
[15.6667,16.0000,-29.5000,'Sco'],
[4.5833,4.7000,-30.0000,'Eri'],
[16.7500,17.6000,-30.0000,'Oph'],
[17.6000,17.8333,-30.0000,'Sgr'],
[10.5833,10.8333,-31.1667,'Hya'],
[6.1167,7.3667,-33.0000,'CMa'],
[12.2500,12.5833,-33.0000,'Hya'],
[10.8333,12.2500,-35.0000,'Hya'],
[3.5000,3.7500,-36.0000,'For'],
[8.3667,9.3667,-36.7500,'Pyx'],
[4.2667,4.5833,-37.0000,'Eri'],
[17.8333,19.1667,-37.0000,'Sgr'],
[21.3333,23.0000,-37.0000,'PsA'],
[23.0000,23.3333,-37.0000,'Scl'],
[3.0000,3.5000,-39.5833,'For'],
[9.3667,11.0000,-39.7500,'Ant'],
[0.0000,1.6667,-40.0000,'Scl'],
[1.6667,3.0000,-40.0000,'For'],
[3.8667,4.2667,-40.0000,'Eri'],
[23.3333,24.0000,-40.0000,'Scl'],
[14.1667,14.9167,-42.0000,'Cen'],
[15.6667,16.0000,-42.0000,'Lup'],
[16.0000,16.4208,-42.0000,'Sco'],
[4.8333,5.0000,-43.0000,'Cae'],
[5.0000,6.5833,-43.0000,'Col'],
[8.0000,8.3667,-43.0000,'Pup'],
[3.4167,3.8667,-44.0000,'Eri'],
[16.4208,17.8333,-45.5000,'Sco'],
[17.8333,19.1667,-45.5000,'CrA'],
[19.1667,20.3333,-45.5000,'Sgr'],
[20.3333,21.3333,-45.5000,'Mic'],
[3.0000,3.4167,-46.0000,'Eri'],
[4.5000,4.8333,-46.5000,'Cae'],
[15.3333,15.6667,-48.0000,'Lup'],
[0.0000,2.3333,-48.1667,'Phe'],
[2.6667,3.0000,-49.0000,'Eri'],
[4.0833,4.2667,-49.0000,'Hor'],
[4.2667,4.5000,-49.0000,'Cae'],
[21.3333,22.0000,-50.0000,'Gru'],
[6.0000,8.0000,-50.7500,'Pup'],
[8.0000,8.1667,-50.7500,'Vel'],
[2.4167,2.6667,-51.0000,'Eri'],
[3.8333,4.0833,-51.0000,'Hor'],
[0.0000,1.8333,-51.5000,'Phe'],
[6.0000,6.1667,-52.5000,'Car'],
[8.1667,8.4500,-53.0000,'Vel'],
[3.5000,3.8333,-53.1667,'Hor'],
[3.8333,4.0000,-53.1667,'Dor'],
[0.0000,1.5833,-53.5000,'Phe'],
[2.1667,2.4167,-54.0000,'Eri'],
[4.5000,5.0000,-54.0000,'Pic'],
[15.0500,15.3333,-54.0000,'Lup'],
[8.4500,8.8333,-54.5000,'Vel'],
[6.1667,6.5000,-55.0000,'Car'],
[11.8333,12.8333,-55.0000,'Cen'],
[14.1667,15.0500,-55.0000,'Lup'],
[15.0500,15.3333,-55.0000,'Nor'],
[4.0000,4.3333,-56.5000,'Dor'],
[8.8333,11.0000,-56.5000,'Vel'],
[11.0000,11.2500,-56.5000,'Cen'],
[17.5000,18.0000,-57.0000,'Ara'],
[18.0000,20.3333,-57.0000,'Tel'],
[22.0000,23.3333,-57.0000,'Gru'],
[3.2000,3.5000,-57.5000,'Hor'],
[5.0000,5.5000,-57.5000,'Pic'],
[6.5000,6.8333,-58.0000,'Car'],
[0.0000,1.3333,-58.5000,'Phe'],
[1.3333,2.1667,-58.5000,'Eri'],
[23.3333,24.0000,-58.5000,'Phe'],
[4.3333,4.5833,-59.0000,'Dor'],
[15.3333,16.4208,-60.0000,'Nor'],
[20.3333,21.3333,-60.0000,'Ind'],
[5.5000,6.0000,-61.0000,'Pic'],
[15.1667,15.3333,-61.0000,'Cir'],
[16.4208,16.5833,-61.0000,'Ara'],
[14.9167,15.1667,-63.5833,'Cir'],
[16.5833,16.7500,-63.5833,'Ara'],
[6.0000,6.8333,-64.0000,'Pic'],
[6.8333,9.0333,-64.0000,'Car'],
[11.2500,11.8333,-64.0000,'Cen'],
[11.8333,12.8333,-64.0000,'Cru'],
[12.8333,14.5333,-64.0000,'Cen'],
[13.5000,13.6667,-65.0000,'Cir'],
[16.7500,16.8333,-65.0000,'Ara'],
[2.1667,3.2000,-67.5000,'Hor'],
[3.2000,4.5833,-67.5000,'Ret'],
[14.7500,14.9167,-67.5000,'Cir'],
[16.8333,17.5000,-67.5000,'Ara'],
[17.5000,18.0000,-67.5000,'Pav'],
[22.0000,23.3333,-67.5000,'Tuc'],
[4.5833,6.5833,-70.0000,'Dor'],
[13.6667,14.7500,-70.0000,'Cir'],
[14.7500,17.0000,-70.0000,'TrA'],
[0.0000,1.3333,-75.0000,'Tuc'],
[3.5000,4.5833,-75.0000,'Hyi'],
[6.5833,9.0333,-75.0000,'Vol'],
[9.0333,11.2500,-75.0000,'Car'],
[11.2500,13.6667,-75.0000,'Mus'],
[18.0000,21.3333,-75.0000,'Pav'],
[21.3333,23.3333,-75.0000,'Ind'],
[23.3333,24.0000,-75.0000,'Tuc'],
[0.7500,1.3333,-76.0000,'Tuc'],
[0.0000,3.5000,-82.5000,'Hyi'],
[7.6667,13.6667,-82.5000,'Cha'],
[13.6667,18.0000,-82.5000,'Aps'],
[3.5000,7.6667,-85.0000,'Men'],
[0.0000,24.0000,-90.0000,'Oct']
];

//
// Input: coordinates (RA in hours, declination in degrees, epoch in years AD)
// Output: constellation abbreviation (3 letters), or '' on error
//
function get_name(ra, dec, epoch)
{
  var convh, convd, newcoords;

  convh = Math.PI / 12.0;
  convd = Math.PI / 180.0;
  ra *= convh;
  dec *= convd;
  newcoords = precess(ra, dec, epoch, 1875.0);
  ra = newcoords[0];
  dec = newcoords[1];
  ra /= convh;
  dec /= convd;
  for (var i = 0; i < table.length; i++)
  {
    if (dec < table[i][2] || ra < table[i][0] || ra >= table[i][1])
       continue;
    return table[i][3];
  }
  return '';    // Error!
}

//
// Input: coordinate string of the form "RA Dec",
// where RA is HH, HH MM, or HH MM SS;
//       Dec is +-DD, +-DD MM, or +-DD MM SS
// Output: [RA, Dec] in hours and degrees, or [] on error
//
function parse_coordinates(str)
{
  var exploded;
  var nra, ndec;
  var rah = 0.0;
  var ram = 0.0;
  var ras = 0.0;
  var decd = 0.0;
  var decm = 0.0;
  var decs = 0.0;

  // Trim leading and trailing whitespace
  str = str.replace(/^\s+/, '');
  str = str.replace(/\s+$/, '');

  // Change Unicode minus sign to hyphen
  str = str.replace(/\u2212/, '-');

  // Split into words separated by whitespace
  exploded = str.split(/\s+/);
  for (nra = 0; nra < exploded.length; nra++)
      if (exploded[nra].length > 0 && 
          (exploded[nra].charAt(0) == '+' || exploded[nra].charAt(0) == '-'))
          break;

  ndec = exploded.length - nra;

  if (nra < 1 || nra > 3 || ndec < 1 || ndec > 3)
     return [];

  rah = parseFloat(exploded[0]);
  if (nra >= 2)
     ram = parseFloat(exploded[1]);
  if (nra >= 3)
     ras = parseFloat(exploded[2]);

  decd = parseFloat(exploded[nra]);
  if (ndec >= 2)
     decm = parseFloat(exploded[nra + 1]);
  if (ndec >= 3)
     decs = parseFloat(exploded[nra + 2]);

  if (isNaN(rah) || isNaN(ram) || isNaN(ras) || isNaN(decd) || isNaN(decm) || isNaN(decs))
     return [];

  if (rah < 0.0 || rah >= 24.0 || ram < 0.0 || ram >= 60.0 || ras < 0.0 || ras >= 60.0)
     return [];

  if (decd < -90.0 || decd > 90.0 || decm < 0.0 || decm >= 60.0 || decs < 0.0 || decs >= 60.0)
     return [];

  if (decd < 0.0 ||
      (decd == 0.0 && exploded[nra].length > 0 && 
       exploded[nra].charAt(0) == '-'))
  {
    decm = -decm;
    decs = -decs;
  }

  return [rah + ram / 60.0 + ras / 3600.0, decd + decm / 60.0 + decs / 3600.0];
}

// The 88 constellation abbreviations and their full names and genitives
var abbrev_table =
[
['And','Andromeda','Andromedae'],
['Ant','Antlia','Antliae'],
['Aps','Apus','Apodis'],
['Aql','Aquila','Aquilae'],
['Aqr','Aquarius','Aquarii'],
['Ara','Ara','Arae'],
['Ari','Aries','Arietis'],
['Aur','Auriga','Aurigae'],
['Boo','Bo\u00f6tes','Bo\u00f6tis'],
['CMa','Canis Major','Canis Majoris'],
['CMi','Canis Minor','Canis Minoris'],
['CVn','Canes Venatici','Canum Venaticorum'],
['Cae','Caelum','Caeli'],
['Cam','Camelopardalis','Camelopardalis'],
['Cap','Capricornus','Capricorni'],
['Car','Carina','Carinae'],
['Cas','Cassiopeia','Cassiopeiae'],
['Cen','Centaurus','Centauri'],
['Cep','Cepheus','Cephei'],
['Cet','Cetus','Ceti'],
['Cha','Chamaeleon','Chamaeleontis'],
['Cir','Circinus','Circini'],
['Cnc','Cancer','Cancri'],
['Col','Columba','Columbae'],
['Com','Coma Berenices','Comae Berenices'],
['CrA','Corona Australis','Coronae Australis'],
['CrB','Corona Borealis','Coronae Borealis'],
['Crt','Crater','Crateris'],
['Cru','Crux','Crucis'],
['Crv','Corvus','Corvi'],
['Cyg','Cygnus','Cygni'],
['Del','Delphinus','Delphini'],
['Dor','Dorado','Doradus'],
['Dra','Draco','Draconis'],
['Equ','Equuleus','Equulei'],
['Eri','Eridanus','Eridani'],
['For','Fornax','Fornacis'],
['Gem','Gemini','Geminorum'],
['Gru','Grus','Gruis'],
['Her','Hercules','Herculis'],
['Hor','Horologium','Horologii'],
['Hya','Hydra','Hydrae'],
['Hyi','Hydrus','Hydri'],
['Ind','Indus','Indi'],
['LMi','Leo Minor','Leonis Minoris'],
['Lac','Lacerta','Lacertae'],
['Leo','Leo','Leonis'],
['Lep','Lepus','Leporis'],
['Lib','Libra','Librae'],
['Lup','Lupus','Lupi'],
['Lyn','Lynx','Lyncis'],
['Lyr','Lyra','Lyrae'],
['Men','Mensa','Mensae'],
['Mic','Microscopium','Microscopii'],
['Mon','Monoceros','Monocerotis'],
['Mus','Musca','Muscae'],
['Nor','Norma','Normae'],
['Oct','Octans','Octantis'],
['Oph','Ophiuchus','Ophiuchi'],
['Ori','Orion','Orionis'],
['Pav','Pavo','Pavonis'],
['Peg','Pegasus','Pegasi'],
['Per','Perseus','Persei'],
['Phe','Phoenix','Phoenicis'],
['Pic','Pictor','Pictoris'],
['PsA','Piscis Austrinus','Piscis Austrini'],
['Psc','Pisces','Piscium'],
['Pup','Puppis','Puppis'],
['Pyx','Pyxis','Pyxidis'],
['Ret','Reticulum','Reticuli'],
['Scl','Sculptor','Sculptoris'],
['Sco','Scorpius','Scorpii'],
['Sct','Scutum','Scuti'],
['Ser','Serpens','Serpentis'],
['Sex','Sextans','Sextantis'],
['Sge','Sagitta','Sagittae'],
['Sgr','Sagittarius','Sagittarii'],
['Tau','Taurus','Tauri'],
['Tel','Telescopium','Telescopii'],
['TrA','Triangulum Australe','Trianguli Australis'],
['Tri','Triangulum','Trianguli'],
['Tuc','Tucana','Tucanae'],
['UMa','Ursa Major','Ursae Majoris'],
['UMi','Ursa Minor','Ursae Minoris'],
['Vel','Vela','Velorum'],
['Vir','Virgo','Virginis'],
['Vol','Volans','Volantis'],
['Vul','Vulpecula','Vulpeculae']
];

//
// Input: coordinate string as above, assumed to be a position in equinox 2000.0 coordinates
// Output: Informative message about its location
//
function main(str)
{
  var coordlist, ra, dec, i, n;

  coordlist = parse_coordinates(str);

  if (coordlist.length == 0)
     return 'Error in coordinates.';
  ra = coordlist[0];
  dec = coordlist[1];  
  n = get_name(ra, dec, 2000.0);
  for (var i = 0; i < abbrev_table.length; i++)
      if (n == abbrev_table[i][0])
          break;
  if (i == abbrev_table.length)
     return 'Error; no constellation found.';
  return 'Constellation: ' + abbrev_table[i][1] + ' (genitive: ' + abbrev_table[i][2] + '; abbreviation: ' + n + ')';
}