144 lines
4.2 KiB
JavaScript
144 lines
4.2 KiB
JavaScript
'use strict';
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Object.defineProperty(exports, '__esModule', { value: true });
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var base = require('./base.cjs');
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/**
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* @copyright 2013 Sonia Keys
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* @copyright 2016 commenthol
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* @license MIT
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* @module moonillum
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*/
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const D2R = Math.PI / 180;
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/**
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* phaseAngleEquatorial computes the phase angle of the Moon given equatorial coordinates.
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*
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* @param {Coord} cMoon - geocentric right ascension, declination and distance to the Moon
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* @param {Coord} cSun - coordinates and distance of the Sun
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* @returns {number} phase angle of the Moon in radians
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*/
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function phaseAngleEquatorial (cMoon, cSun) {
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return pa(cMoon.range, cSun.range, cosEq(cMoon.ra, cMoon.dec, cSun.ra, cSun.dec))
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}
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/**
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* cos elongation from equatorial coordinates
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* @private
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*/
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function cosEq (α, δ, α0, δ0) {
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const [sδ, cδ] = base["default"].sincos(δ);
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const [sδ0, cδ0] = base["default"].sincos(δ0);
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return sδ0 * sδ + cδ0 * cδ * Math.cos(α0 - α)
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}
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/**
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* phase angle from cos elongation and distances
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* @private
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* @param {number} Δ
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* @param {number} R
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* @param {number} cψ
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* @returns {number}
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*/
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function pa (Δ, R, cψ) {
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const sψ = Math.sin(Math.acos(cψ));
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let i = Math.atan(R * sψ / (Δ - R * cψ));
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if (i < 0) {
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i += Math.PI;
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}
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return i
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}
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/**
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* phaseAngleEquatorial2 computes the phase angle of the Moon given equatorial coordinates.
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*
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* Less accurate than phaseAngleEquatorial.
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*
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* Arguments α, δ are geocentric right ascension and declination of the Moon;
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* α0, δ0 are coordinates of the Sun. Angles must be in radians.
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*
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* @param {Coord} cMoon - eocentric right ascension and declination of the Moon
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* @param {Coord} cSun - coordinates of the Sun
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* @returns {number} phase angle of the Moon in radians
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*/
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function phaseAngleEquatorial2 (cMoon, cSun) {
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return Math.acos(-cosEq(cMoon.ra, cMoon.dec, cSun.ra, cSun.dec))
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}
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/**
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* phaseAngleEcliptic computes the phase angle of the Moon given ecliptic coordinates.
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*
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* Distances must be in the same units as each other.
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*
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* @param {Coord} cMoon - geocentric longitude, latitude and distance to the Moon
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* @param {Coord} cSun - longitude and distance to the Sun
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* @returns {number} phase angle of the Moon in radians
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*/
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function phaseAngleEcliptic (cMoon, cSun) {
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return pa(cMoon.range, cSun.range, cosEcl(cMoon.lon, cMoon.lat, cSun.lon))
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}
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/**
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* cos elongation from ecliptic coordinates
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* @private
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*/
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function cosEcl (λ, β, λ0) { // (λ, β, λ0 float64) float64
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return Math.cos(β) * Math.cos(λ - λ0)
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}
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/**
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* phaseAngleEcliptic2 computes the phase angle of the Moon given ecliptic coordinates.
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*
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* Less accurate than phaseAngleEcliptic.
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*
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* Angles must be in radians.
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*
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* @param {Coord} cMoon - geocentric longitude, latitude of the Moon
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* @param {Coord} cSun - longitude of the Sun
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* @returns {number} phase angle of the Moon in radians
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*/
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function phaseAngleEcliptic2 (cMoon, cSun) {
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return Math.acos(-cosEcl(cMoon.lon, cMoon.lat, cSun.lon))
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}
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/**
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* phaseAngle3 computes the phase angle of the Moon given a julian day.
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*
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* Less accurate than phaseAngle functions taking coordinates.
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*
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* Result in radians.
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*/
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function phaseAngle3 (jde) { // (jde float64) float64
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const T = base["default"].J2000Century(jde);
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const D = base["default"].horner(T, 297.8501921 * D2R, 445267.1114034 * D2R,
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-0.0018819 * D2R, D2R / 545868, -D2R / 113065000);
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const m = base["default"].horner(T, 357.5291092 * D2R, 35999.0502909 * D2R,
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-0.0001536 * D2R, D2R / 24490000);
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const m_ = base["default"].horner(T, 134.9633964 * D2R, 477198.8675055 * D2R,
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0.0087414 * D2R, D2R / 69699, -D2R / 14712000);
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return Math.PI - base["default"].pmod(D, 2 * Math.PI) +
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-6.289 * D2R * Math.sin(m_) +
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2.1 * D2R * Math.sin(m) +
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-1.274 * D2R * Math.sin(2 * D - m_) +
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-0.658 * D2R * Math.sin(2 * D) +
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-0.214 * D2R * Math.sin(2 * m_) +
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-0.11 * D2R * Math.sin(D)
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}
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var moonillum = {
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phaseAngleEquatorial,
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phaseAngleEquatorial2,
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phaseAngleEcliptic,
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phaseAngleEcliptic2,
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phaseAngle3
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};
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exports["default"] = moonillum;
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exports.phaseAngle3 = phaseAngle3;
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exports.phaseAngleEcliptic = phaseAngleEcliptic;
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exports.phaseAngleEcliptic2 = phaseAngleEcliptic2;
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exports.phaseAngleEquatorial = phaseAngleEquatorial;
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exports.phaseAngleEquatorial2 = phaseAngleEquatorial2;
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