[Help Wanted] Moon Phase computation

Hi,

First of all, thanks for your library. I am not exploring yet, but it's definitively quite something !

Using your library, I am trying to reproduce the following moon phase indicator : http://www.patek.com/en/collection/movements-complications/moonphase-indicator

For now, I've something like this:

    this.illum = this.getMoonIllumination(new Date());
    this.pos = this.getMoonPosition(new Date(), 0, 0);
    this.angleMoon = this.illum.angle - this.pos.parallacticAngle;

Which gives me the actual moon position at Date() rather than the moon phase.

I've tried to adapt the calculation so they match this code by Xavier Jubier, without success:

/**
 * The following code is
 * Adapted from http://xjubier.free.fr/en/site_pages/LunarEclipseCalculator.html
 * Copyright Xavier Jubier
 */
var myPhaseName = "";
var forecastImage = new Array();

function moonPhasePercent(theDate)
{
  var synodic = 29.53058867;
  var msPerDay = 86400000;
  var baseDate = new Date();
  baseDate.setUTCFullYear(2005);
  baseDate.setUTCMonth(4);
  baseDate.setUTCDate(8);
  baseDate.setUTCHours(8);
  baseDate.setUTCMinutes(48);

  var diff = theDate - baseDate;
  var phase = diff / (synodic * msPerDay);
  phase *= 100;
  phase %= 100;
  if ( phase < 0 )
    phase += 100;

  return(phase);
}

function getMoonPhase()
{

  var theDate = new Date();

  var phasePercent = moonPhasePercent(theDate);

  var phaseNames = [
    "New Moon", "New Moon",
    "Waxing Crescent", "Waxing Crescent", "Waxing Crescent", "Waxing Crescent",
    "First Quarter", "First Quarter", "First Quarter",
    "Waxing Gibbous", "Waxing Gibbous", "Waxing Gibbous", "Waxing Gibbous", "Waxing Gibbous",
    "Full Moon", "Full Moon",
    "Waning Gibbous", "Waning Gibbous", "Waning Gibbous", "Waning Gibbous",
    "Last Quarter", "Last Quarter", "Last Quarter",
    "Waning Crescent", "Waning Crescent", "Waning Crescent", "Waning Crescent",
    "New Moon"
  ];

  thePhase = Math.round(phasePercent * 0.279);
  myPhaseName = phaseNames[thePhase];

  return thePhase;
}

Thanks, M.

slowe / astro.js

[Help Wanted] Moon Phase computation #1