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suncalc.js
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suncalc.js
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(function () { 'use strict';
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;
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; }
var e = rad * 23.4397;
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)
h = 0;
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)),
P = rad * 102.9372;
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 = {};
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)
};
};
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]);
};
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);
}
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;
};
function moonCoords(d) {
var L = rad * (218.316 + 13.176396 * d),
M = rad * (134.963 + 13.064993 * d),
F = rad * (93.272 + 13.229350 * d),
l = L + rad * 6.289 * sin(M),
b = rad * 5.128 * sin(F),
dt = 385001 - 20905 * cos(M);
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),
pa = atan(sin(H), tan(phi) * cos(c.dec) - sin(c.dec) * cos(H));
h = h + astroRefraction(h);
return {
azimuth: azimuth(H, phi, c.dec),
altitude: h,
distance: c.dist,
parallacticAngle: pa
};
};
SunCalc.getMoonIllumination = function (date) {
var d = toDays(date || new Date()),
s = sunCoords(d),
m = moonCoords(d),
sdist = 149598000,
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);
}
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;
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;
};
if (typeof exports === 'object' && typeof module !== 'undefined') module.exports = SunCalc;
else if (typeof define === 'function' && define.amd) define(SunCalc);
else window.SunCalc = SunCalc;
}());