CALCULER LA PHASE DE LA LUNE - MOON PHASE

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/*
Adaptation en php du fameux et excellent scripte Astro-MoonPhase de Brett Hamilton écrit en Perl.
http://search.cpan.org/~brett/Astro-MoonPhase-0.60/

Ce Scripte vous permettra de connaître, à une date donnée, l'illumination de la Lune, son age, 
sa distance en km par rapport à la Terre, son angle en degrés, sa distance par rapport au soleil, 
et son angle par rapport au soleil.

*/
class Moon
	{
	function phase($Year, $Month, $Day, $Hour, $Minutes, $Seconds)
		{
		$DateSec = mktime($Hour, $Minutes, $Seconds, $Month, $Day, $Year, 0);

		ini_set(precision, "20");	//Defini la precision des calcules

		# Astronomical constants.
		$Epoch					= 2444238.5;		# 1980 January 0.0

		# Constants defining the Sun's apparent orbit.
		$Elonge					= 278.833540;		# ecliptic longitude of the Sun at epoch 1980.0
		$Elongp					= 282.596403;		# ecliptic longitude of the Sun at perigee
		$Eccent					= 0.016718;			# eccentricity of Earth's orbit
		$Sunsmax				= 1.495985e8;		# semi-major axis of Earth's orbit, km
		$Sunangsiz				= 0.533128;			# sun's angular size, degrees, at semi-major axis distance

		# Elements of the Moon's orbit, epoch 1980.0.
		$Mmlong					= 64.975464;		# moon's mean longitude at the epoch
		$Mmlongp				= 349.383063;		# mean longitude of the perigee at the epoch
		$Mlnode					= 151.950429;		# mean longitude of the node at the epoch
		$Minc					= 5.145396;			# inclination of the Moon's orbit
		$Mecc					= 0.054900;			# eccentricity of the Moon's orbit
		$Mangsiz				= 0.5181;			# moon's angular size at distance a from Earth
		$Msmax					= 384401.0;			# semi-major axis of Moon's orbit in km
		$Mparallax				= 0.9507;			# parallax at distance a from Earth
		$Synmonth				= 29.53058868;		# synodic month (new Moon to new Moon)

		$pdate = Moon::jtime($DateSec);

		$pphase;				# illuminated fraction
		$mage;					# age of moon in days
		$dist;					# distance in kilometres
		$angdia;				# angular diameter in degrees
		$sudist;				# distance to Sun
		$suangdia;				# sun's angular diameter


		# Calculation of the Sun's position.

		$Day = $pdate - $Epoch;										# date within epoch
		$N = Moon::fixangle((360 / 365.2422) * $Day);				# mean anomaly of the Sun
		$M = Moon::fixangle($N + $Elonge - $Elongp);				# convert from perigee
										# co-ordinates to epoch 1980.0
		$Ec = Moon::kepler($M, $Eccent);							# solve equation of Kepler
		$Ec = sqrt((1 + $Eccent) / (1 - $Eccent)) * tan($Ec / 2);
		$Ec = 2 * Moon::todeg(atan($Ec));							# true anomaly
		$Lambdasun = Moon::fixangle($Ec + $Elongp);					# Sun's geocentric ecliptic
										# longitude
		# Orbital distance factor.
		$F = ((1 + $Eccent * cos(Moon::torad($Ec))) / (1 - $Eccent * $Eccent));
		$SunDist = $Sunsmax / $F;									# distance to Sun in km
		$SunAng = $F * $Sunangsiz;									# Sun's angular size in degrees


		# Calculation of the Moon's position.

		# Moon's mean longitude.
		$ml = Moon::fixangle(13.1763966 * $Day + $Mmlong);

		# Moon's mean anomaly.
		$MM = Moon::fixangle($ml - 0.1114041 * $Day - $Mmlongp);

		# Moon's ascending node mean longitude.
		$MN = Moon::fixangle($Mlnode - 0.0529539 * $Day);

		# Evection.
		$Ev = 1.2739 * sin(Moon::torad(2 * ($ml - $Lambdasun) - $MM));

		# Annual equation.
		$Ae = 0.1858 * sin(Moon::torad($M));

		# Correction term.
		$A3 = 0.37 * sin(Moon::torad($M));

		# Corrected anomaly.
		$MmP = $MM + $Ev - $Ae - $A3;

		# Correction for the equation of the centre.
		$mEc = 6.2886 * sin(Moon::torad($MmP));

		# Another correction term.
		$A4 = 0.214 * sin(Moon::torad(2 * $MmP));

		# Corrected longitude.
		$lP = $ml + $Ev + $mEc - $Ae + $A4;

		# Variation.
		$V = 0.6583 * sin(Moon::torad(2 * ($lP - $Lambdasun)));

		# True longitude.
		$lPP = $lP + $V;

		# Corrected longitude of the node.
		$NP = $MN - 0.16 * sin(Moon::torad($M));

		# Y inclination coordinate.
		$y = sin(Moon::torad($lPP - $NP)) * cos(Moon::torad($Minc));

		# X inclination coordinate.
		$x = cos(Moon::torad($lPP - $NP));

		# Ecliptic longitude.
		$Lambdamoon = Moon::todeg(atan2($y, $x));
		$Lambdamoon += $NP;

		# Ecliptic latitude.
		$BetaM = Moon::todeg(asin(sin(Moon::torad($lPP - $NP)) * sin(Moon::torad($Minc))));

		# Calculation of the phase of the Moon.

		# Age of the Moon in degrees.
		$MoonAge = $lPP - $Lambdasun;

		# Phase of the Moon.
		$MoonPhase = (1 - cos(Moon::torad($MoonAge))) / 2;

		# Calculate distance of moon from the centre of the Earth.

		$MoonDist = ($Msmax * (1 - $Mecc * $Mecc)) /
			(1 + $Mecc * cos(Moon::torad($MmP + $mEc)));

		# Calculate Moon's angular diameter.

		$MoonDFrac = $MoonDist / $Msmax;
		$MoonAng = $Mangsiz / $MoonDFrac;

		# Calculate Moon's parallax.

		$MoonPar = $Mparallax / $MoonDFrac;
		
		$pphase = $MoonPhase;									# illuminated fraction
		$mage = $Synmonth * (Moon::fixangle($MoonAge) / 360.0);	# age of moon in days
		$dist = $MoonDist;										# distance in kilometres
		$angdia = $MoonAng;										# angular diameter in degrees
		$sudist = $SunDist;										# distance to Sun
		$suangdia = $SunAng;									# sun's angular diameter
		$mpfrac = Moon::fixangle($MoonAge) / 360.0;
		return array( $pphase, $mage, $dist, $angdia, $sudist, $suangdia, $mpfrac, $mpfrac );
		}

	function fixangle($x)	{ return ($x - 360.0 * (floor($x / 360.0))); }	# fix angle
	function torad($x)	{ return ($x * (M_PI / 180.0)); }				# deg->rad
	function todeg($x)	{ return ($x * (180.0 / M_PI)); }				# rad->deg

	function jtime($t)
		{
		$julian = ($t / 86400) + 2440587.5;	# (seconds /(seconds per day)) + julian date of epoch		2440587.5 / 86400 = 28,24753472222 Days
		return ($julian);
		}

	function kepler($m, $ecc)
		{
		$EPSILON = 1e-6;

		$m = Moon::torad($m);
		$e = $m;
		while (abs($delta) > $EPSILON)
			{
			$delta = $e - $ecc * sin($e) - $m;
			$e -= $delta / (1 - $ecc * cos($e));
			}
		return ($e);
		}

	}
	
	
//Exemple d'utilisation :

//Pour le 11 Avril 2009 à 00h00
list($MoonPhase, $MoonAge, $MoonDist, $MoonAng, $SunDist, $SunAng, $mpfrac) = Moon::phase(2009, 04, 11, 00, 00, 01);
echo "La Lune est éclairée à ".number_format($MoonPhase*100, 2, ',', '')."%"."<br>";
echo "Son age est de ".number_format($MoonAge, 0, ',', '')." jours"."<br>";
echo "Et elle se situe à une distance de ".number_format($MoonDist, 0, ',', '')." km par rapport à la Terre."."<br>";


//Vous pouvez voir le scripte en fonctionnement sur www.CropCirclesDataBase.org
//dans la rubrique calendrier.
?>