Lunar phase

Calculate phase of the moon using Julian date.

Getting Started

To install, execute:

npm i lunarphase-js

Then, import into a project as:

import { Moon } from "lunarphase-js";

Usage

In the lunar calendar there are 8 phases each synodic month, which is the number of days to complete the cycle. This time between two identical syzygies is equivalent to 29.53059 Earth days.

Lunar phases, in order:

Julian Day

Convert to and from Gregorian Dates to Julian Days via the JulianDay module.

API Reference:

To convert a date to Julian Day:

import { JulianDay } from "lunarphase-js";

const date = new Date();
const julian = JulianDay.fromDate(date);

To convert a Julian Day to a date:

import { JulianDay } from "lunarphase-js";

const julian = 2459356.529302257;
const date = JulianDay.toDate(julian);

Lunar Phases

API Reference:

For a specific date, pass a date object to a function

import { Moon } from "lunarphase-js";

const date = new Date();
const phase = Moon.lunarPhase(date);

Otherwise, current date will be used

import { Moon } from "lunarphase-js";

const phase = Moon.lunarPhase();

Lunar Phase

To get the current lunar phase from the LunarPhase enum (ex: "FULL")

const phase = Moon.lunarPhase();

Lunar Phase Emoji

To get the current lunar phase emoji from the LunarEmoji (ex: "🌕"):

const phaseEmoji = Moon.lunarPhaseEmoji();

As phases are inverted between Northern and Southern Hemispheres, optionally pass a Hemisphere to the function:

import { Moon } from "lunarphase-js";
import { Hemisphere } from "lunarphase-js";

const date = new Date();
Moon.lunarPhaseEmoji(date, Hemisphere.NORTHERN);

To get emoji for other lunar phases, pass a LunarPhase enum:

const emoji = Moon.emojiForLunarPhase(Moon.LunarPhase.Full);

Optionally pass a Hemisphere to the function:

import { Moon } from "lunarphase-js";
import { LunarPhase } from "lunarphase-js";
import { Hemisphere } from "lunarphase-js";

Moon.emojiForLunarPhase(LunarPhase.FIRST_QUARTER, Hemisphere.SOUTHERN);

Waxing

Whether the moon is waxing (ex: false)

const waxing = Moon.isWaxing();

Waning

Whether the moon is waning (ex: true)

const waning = Moon.isWaning();

Lunar Age

Age in Earth days through the current lunar cycle, equivalent to 29.53059 Earth days, based on Mean Synodic Month, 2000 AD mean solar days.

To get the lunar age (ex: 16.54412413414952)

const age = Moon.lunarAge();

Lunar Age Percent

To get the percentage through the lunar cycle (ex: 0.5602368519132597)

const agePercent = Moon.lunarAgePercent();

Lunation Number

Brown Lunation Number (BLN), per Ernest William Brown's lunar theory, defining Lunation 1 as the first new moon of 1923 at approximately 02:41 UTC, January 17, 1923

const lunationNumber = Moon.lunationNumber();

Lunar Distance

Distance to the moon measured in units of Earth radii, with perigee at 56 and apogee at 63.8.

const distance = Moon.lunarDistance();