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SunCalc

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SunCalc is a tiny BSD-licensed JavaScript library for calculating sun position, sunlight phases (times for sunrise, sunset, dusk, etc.), moon position and lunar phase for the given location and time, created by Vladimir Agafonkin (@mourner) as a part of the SunCalc.net project.

Most calculations are based on the formulas given in the excellent Astronomy Answers articles about position of the sun and the planets. You can read about different twilight phases calculated by SunCalc in the Twilight article on Wikipedia.

Usage example

// get today's sunlight times for London
var times = SunCalc.getTimes(new Date(), 51.5, -0.1);

// format sunrise time from the Date object
var sunriseStr = times.sunrise.getHours() + ':' + times.sunrise.getMinutes();

// get position of the sun (azimuth and altitude) at today's sunrise
var sunrisePos = SunCalc.getPosition(times.sunrise, 51.5, -0.1);

// get sunrise azimuth in degrees
var sunriseAzimuth = sunrisePos.azimuth * 180 / Math.PI;

SunCalc is also available as an NPM package:

$ npm install suncalc
var SunCalc = require('suncalc');

Reference

Sunlight times

SunCalc.getTimes(/*Date*/ date, /*Number*/ latitude, /*Number*/ longitude, /*Number (default=0)*/ height)

Returns an object with the following properties (each is a Date object):

PropertyDescription
sunrisesunrise (top edge of the sun appears on the horizon)
sunriseEndsunrise ends (bottom edge of the sun touches the horizon)
goldenHourEndmorning golden hour (soft light, best time for photography) ends
solarNoonsolar noon (sun is in the highest position)
goldenHourevening golden hour starts
sunsetStartsunset starts (bottom edge of the sun touches the horizon)
sunsetsunset (sun disappears below the horizon, evening civil twilight starts)
duskdusk (evening nautical twilight starts)
nauticalDusknautical dusk (evening astronomical twilight starts)
nightnight starts (dark enough for astronomical observations)
nadirnadir (darkest moment of the night, sun is in the lowest position)
nightEndnight ends (morning astronomical twilight starts)
nauticalDawnnautical dawn (morning nautical twilight starts)
dawndawn (morning nautical twilight ends, morning civil twilight starts)
SunCalc.addTime(/*Number*/ angleInDegrees, /*String*/ morningName, /*String*/ eveningName)

Adds a custom time when the sun reaches the given angle to results returned by SunCalc.getTimes.

SunCalc.times property contains all currently defined times.

Sun position

SunCalc.getPosition(/*Date*/ timeAndDate, /*Number*/ latitude, /*Number*/ longitude)

Returns an object with the following properties:

Moon position

SunCalc.getMoonPosition(/*Date*/ timeAndDate, /*Number*/ latitude, /*Number*/ longitude)

Returns an object with the following properties:

Moon illumination

SunCalc.getMoonIllumination(/*Date*/ timeAndDate)

Returns an object with the following properties:

Moon phase value should be interpreted like this:

PhaseName
0New Moon
Waxing Crescent
0.25First Quarter
Waxing Gibbous
0.5Full Moon
Waning Gibbous
0.75Last Quarter
Waning Crescent

By subtracting the parallacticAngle from the angle one can get the zenith angle of the moons bright limb (anticlockwise). The zenith angle can be used do draw the moon shape from the observers perspective (e.g. moon lying on its back).

Moon rise and set times

SunCalc.getMoonTimes(/*Date*/ date, /*Number*/ latitude, /*Number*/ longitude[, inUTC])

Returns an object with the following properties:

By default, it will search for moon rise and set during local user's day (frou 0 to 24 hours). If inUTC is set to true, it will instead search the specified date from 0 to 24 UTC hours.

Changelog

1.8.0 — Dec 22, 2016

1.7.0 — Nov 11, 2015

1.6.0 — Oct 27, 2014

1.5.1 — May 16, 2014

1.4.0 — Apr 10, 2014

1.3.0 — Feb 21, 2014

1.2.0 — Mar 07, 2013

1.1.0 — Mar 06, 2013

1.0.0 — Dec 07, 2011

0.0.0 — Aug 25, 2011