MediaWiki:SunCalc.js

/* (c) 2011-2014, Vladimir Agafonkin SunCalc is a JavaScript library for calculating sun/mooon position and light phases. https://github.com/mourner/suncalc

(function { 'use strict';

// shortcuts for easier to read formulas

var PI  = Math.PI, sin = Math.sin, cos = Math.cos, tan = Math.tan, asin = Math.asin, atan = Math.atan2, acos = Math.acos, rad = PI / 180;

// sun calculations are based on http://aa.quae.nl/en/reken/zonpositie.html formulas

// date/time constants and conversions

var dayMs = 1000 * 60 * 60 * 24, J1970 = 2440588, J2000 = 2451545;

function toJulian(date) { return date.valueOf / dayMs - 0.5 + J1970; } function fromJulian(j) { return new Date((j + 0.5 - J1970) * dayMs); } function toDays(date)  { return toJulian(date) - J2000; }

// general calculations for position

var e = rad * 23.4397; // obliquity of the Earth

function rightAscension(l, b) { return atan(sin(l) * cos(e) - tan(b) * sin(e), cos(l)); } function declination(l, b)   { return asin(sin(b) * cos(e) + cos(b) * sin(e) * sin(l)); }

function azimuth(H, phi, dec) { return atan(sin(H), cos(H) * sin(phi) - tan(dec) * cos(phi)); } function altitude(H, phi, dec) { return asin(sin(phi) * sin(dec) + cos(phi) * cos(dec) * cos(H)); }

function siderealTime(d, lw) { return rad * (280.16 + 360.9856235 * d) - lw; }

// general sun calculations

function solarMeanAnomaly(d) { return rad * (357.5291 + 0.98560028 * d); }

function eclipticLongitude(M) {

var C = rad * (1.9148 * sin(M) + 0.02 * sin(2 * M) + 0.0003 * sin(3 * M)), // equation of center P = rad * 102.9372; // perihelion of the Earth

return M + C + P + PI; }

function sunCoords(d) {

var M = solarMeanAnomaly(d), L = eclipticLongitude(M);

return { dec: declination(L, 0), ra: rightAscension(L, 0) }; }

var SunCalc = {};

// calculates sun position for a given date and latitude/longitude

SunCalc.getPosition = function (date, lat, lng) {

var lw = rad * -lng, phi = rad * lat, d  = toDays(date),

c = sunCoords(d), H = siderealTime(d, lw) - c.ra;

return { azimuth: azimuth(H, phi, c.dec), altitude: altitude(H, phi, c.dec) }; };

// sun times configuration (angle, morning name, evening name)

var times = SunCalc.times = [ [-0.833, 'sunrise',      'sunset'      ], [ -0.3, 'sunriseEnd',    'sunsetStart' ], [   -6, 'dawn',          'dusk'        ], [  -12, 'nauticalDawn',  'nauticalDusk'], [  -18, 'nightEnd',      'night'       ], [    6, 'goldenHourEnd', 'goldenHour'  ] ];

// adds a custom time to the times config

SunCalc.addTime = function (angle, riseName, setName) { times.push([angle, riseName, setName]); };

// calculations for sun times

var J0 = 0.0009;

function julianCycle(d, lw) { return Math.round(d - J0 - lw / (2 * PI)); }

function approxTransit(Ht, lw, n) { return J0 + (Ht + lw) / (2 * PI) + n; } function solarTransitJ(ds, M, L) { return J2000 + ds + 0.0053 * sin(M) - 0.0069 * sin(2 * L); }

function hourAngle(h, phi, d) { return acos((sin(h) - sin(phi) * sin(d)) / (cos(phi) * cos(d))); }

// returns set time for the given sun altitude function getSetJ(h, lw, phi, dec, n, M, L) {

var w = hourAngle(h, phi, dec), a = approxTransit(w, lw, n); return solarTransitJ(a, M, L); }

// calculates sun times for a given date and latitude/longitude

SunCalc.getTimes = function (date, lat, lng) {

var lw = rad * -lng, phi = rad * lat,

d = toDays(date), n = julianCycle(d, lw), ds = approxTransit(0, lw, n),

M = solarMeanAnomaly(ds), L = eclipticLongitude(M), dec = declination(L, 0),

Jnoon = solarTransitJ(ds, M, L),

i, len, time, Jset, Jrise;

var result = { solarNoon: fromJulian(Jnoon), nadir: fromJulian(Jnoon - 0.5) };

for (i = 0, len = times.length; i < len; i += 1) { time = times[i];

Jset = getSetJ(time[0] * rad, lw, phi, dec, n, M, L); Jrise = Jnoon - (Jset - Jnoon);

result[time[1]] = fromJulian(Jrise); result[time[2]] = fromJulian(Jset); }

return result; };

// moon calculations, based on http://aa.quae.nl/en/reken/hemelpositie.html formulas

function moonCoords(d) { // geocentric ecliptic coordinates of the moon

var L = rad * (218.316 + 13.176396 * d), // ecliptic longitude M = rad * (134.963 + 13.064993 * d), // mean anomaly F = rad * (93.272 + 13.229350 * d), // mean distance

l = L + rad * 6.289 * sin(M), // longitude b = rad * 5.128 * sin(F),     // latitude dt = 385001 - 20905 * cos(M); // distance to the moon in km

return { ra: rightAscension(l, b), dec: declination(l, b), dist: dt   }; }

SunCalc.getMoonPosition = function (date, lat, lng) {

var lw = rad * -lng, phi = rad * lat, d  = toDays(date),

c = moonCoords(d), H = siderealTime(d, lw) - c.ra, h = altitude(H, phi, c.dec);

// altitude correction for refraction h = h + rad * 0.017 / tan(h + rad * 10.26 / (h + rad * 5.10));

return { azimuth: azimuth(H, phi, c.dec), altitude: h,       distance: c.dist }; };

// calculations for illumination parameters of the moon, // based on http://idlastro.gsfc.nasa.gov/ftp/pro/astro/mphase.pro formulas and // Chapter 48 of "Astronomical Algorithms" 2nd edition by Jean Meeus (Willmann-Bell, Richmond) 1998.

SunCalc.getMoonIllumination = function (date) {

var d = toDays(date), s = sunCoords(d), m = moonCoords(d),

sdist = 149598000, // distance from Earth to Sun in km

phi = acos(sin(s.dec) * sin(m.dec) + cos(s.dec) * cos(m.dec) * cos(s.ra - m.ra)), inc = atan(sdist * sin(phi), m.dist - sdist * cos(phi)), angle = atan(cos(s.dec) * sin(s.ra - m.ra), sin(s.dec) * cos(m.dec) -               cos(s.dec) * sin(m.dec) * cos(s.ra - m.ra));

return { fraction: (1 + cos(inc)) / 2, phase: 0.5 + 0.5 * inc * (angle < 0 ? -1 : 1) / Math.PI, angle: angle }; };

function hoursLater(date, h) { return new Date(date.valueOf + h * dayMs / 24); }

// calculations for moon rise/set times are based on http://www.stargazing.net/kepler/moonrise.html article

SunCalc.getMoonTimes = function (date, lat, lng) { var t = new Date(date); t.setHours(0); t.setMinutes(0); t.setSeconds(0); t.setMilliseconds(0);

var hc = 0.133 * rad, h0 = SunCalc.getMoonPosition(t, lat, lng).altitude - hc, h1, h2, rise, set, a, b, xe, ye, d, roots, x1, x2, dx;

// go in 2-hour chunks, each time seeing if a 3-point quadratic curve crosses zero (which means rise or set) for (var i = 1; i <= 24; i += 2) { h1 = SunCalc.getMoonPosition(hoursLater(t, i), lat, lng).altitude - hc; h2 = SunCalc.getMoonPosition(hoursLater(t, i + 1), lat, lng).altitude - hc;

a = (h0 + h2) / 2 - h1; b = (h2 - h0) / 2; xe = -b / (2 * a); ye = (a * xe + b) * xe + h1; d = b * b - 4 * a * h1; roots = 0;

if (d >= 0) { dx = Math.sqrt(d) / (Math.abs(a) * 2); x1 = xe - dx; x2 = xe + dx; if (Math.abs(x1) <= 1) roots++; if (Math.abs(x2) <= 1) roots++; if (x1 < -1) x1 = x2; }

if (roots === 1) { if (h0 < 0) rise = i + x1; else set = i + x1;

} else if (roots === 2) { rise = i + (ye < 0 ? x2 : x1); set = i + (ye < 0 ? x1 : x2); }

if (rise && set) break;

h0 = h2; }

var result = {};

if (rise) result.rise = hoursLater(t, rise); if (set) result.set = hoursLater(t, set);

if (!rise && !set) result[ye > 0 ? 'alwaysUp' : 'alwaysDown'] = true;

return result; };

// export as AMD module / Node module / browser variable if (typeof define === 'function' && define.amd) define(SunCalc); else if (typeof module !== 'undefined') module.exports = SunCalc; else window.SunCalc = SunCalc;

});