/* (c) 2011-2015, Vladimir Agafonkin SunCalc is a JavaScript library for calculating sun/moon 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; } function astroRefraction(h) { if (h < 0) // the following formula works for positive altitudes only. h = 0; // if h = -0.08901179 a div/0 would occur. // formula 16.4 of "Astronomical Algorithms" 2nd edition by Jean Meeus (Willmann-Bell, Richmond) 1998. // 1.02 / tan(h + 10.26 / (h + 5.10)) h in degrees, result in arc minutes -> converted to rad: return 0.0002967 / Math.tan(h + 0.00312536 / (h + 0.08901179)); } // 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))); } function observerAngle(height) { return -2.076 * Math.sqrt(height) / 60; } // 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, latitude/longitude, and, optionally, // the observer height (in meters) relative to the horizon SunCalc.getTimes = function (date, lat, lng, height) { height = height || 0; var lw = rad * -lng, phi = rad * lat, dh = observerAngle(height), 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, h0, 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]; h0 = (time[0] + dh) * rad; Jset = getSetJ(h0, 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), // formula 14.1 of "Astronomical Algorithms" 2nd edition by Jean Meeus (Willmann-Bell, Richmond) 1998. pa = atan(sin(H), tan(phi) * cos(c.dec) - sin(c.dec) * cos(H)); h = h + astroRefraction(h); // altitude correction for refraction return { azimuth: azimuth(H, phi, c.dec), altitude: h, distance: c.dist, parallacticAngle: pa }; }; // 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 || new 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, inUTC) { var t = new Date(date); if (inUTC) t.setUTCHours(0, 0, 0, 0); else t.setHours(0, 0, 0, 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 Node module / AMD module / browser variable if (typeof exports === 'object' && typeof module !== 'undefined') module.exports = SunCalc; else if (typeof define === 'function' && define.amd) define(SunCalc); else window.SunCalc = SunCalc; }());