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1'use strict';
2
3Object.defineProperty(exports, "__esModule", {
4 value: true
5});
6
7var _slicedToArray = function () { function sliceIterator(arr, i) { var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"]) _i["return"](); } finally { if (_d) throw _e; } } return _arr; } return function (arr, i) { if (Array.isArray(arr)) { return arr; } else if (Symbol.iterator in Object(arr)) { return sliceIterator(arr, i); } else { throw new TypeError("Invalid attempt to destructure non-iterable instance"); } }; }(); /**
8 * @copyright 2013 Sonia Keys
9 * @copyright 2016 commenthol
10 * @license MIT
11 * @module moonillum
12 */
13/**
14 * Moonillum: Chapter 48, Illuminated Fraction of the Moon's Disk
15 *
16 * Also see functions `illuminated` and `limb` in package base. The function
17 * for computing illuminated fraction given a phase angle (48.1) is
18 * base.illuminated. Formula (48.3) is implemented as base.limb.
19 */
20
21exports.phaseAngleEquatorial = phaseAngleEquatorial;
22exports.phaseAngleEquatorial2 = phaseAngleEquatorial2;
23exports.phaseAngleEcliptic = phaseAngleEcliptic;
24exports.phaseAngleEcliptic2 = phaseAngleEcliptic2;
25exports.phaseAngle3 = phaseAngle3;
26
27var _base = require('./base');
28
29var _base2 = _interopRequireDefault(_base);
30
31function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
32
33var p = Math.PI / 180;
34
35/**
36 * phaseAngleEquatorial computes the phase angle of the Moon given equatorial coordinates.
37 *
38 * @param {base.Coord} cMoon - geocentric right ascension, declination and distance to the Moon
39 * @param {base.Coord} cSun - coordinates and distance of the Sun
40 * @returns {number} phase angle of the Moon in radians
41 */
42function phaseAngleEquatorial(cMoon, cSun) {
43 return pa(cMoon.range, cSun.range, cosEq(cMoon.ra, cMoon.dec, cSun.ra, cSun.dec));
44}
45
46/**
47 * cos elongation from equatorial coordinates
48 * @private
49 */
50function cosEq(α, δ, α0, δ0) {
51 var _base$sincos = _base2.default.sincos(δ),
52 _base$sincos2 = _slicedToArray(_base$sincos, 2),
53 sδ = _base$sincos2[0],
54 cδ = _base$sincos2[1];
55
56 var _base$sincos3 = _base2.default.sincos(δ0),
57 _base$sincos4 = _slicedToArray(_base$sincos3, 2),
58 sδ0 = _base$sincos4[0],
59 cδ0 = _base$sincos4[1];
60
61 return sδ0 * sδ + cδ0 * cδ * Math.cos(α0 - α);
62}
63
64/**
65 * phase angle from cos elongation and distances
66 * @private
67 * @param {number} Δ
68 * @param {number} R
69 * @param {number} cψ
70 * @returns {number}
71 */
72function pa(Δ, R, cψ) {
73 var sψ = Math.sin(Math.acos(cψ));
74 var i = Math.atan(R * sψ / (Δ - R * cψ));
75 if (i < 0) {
76 i += Math.PI;
77 }
78 return i;
79}
80
81/**
82 * phaseAngleEquatorial2 computes the phase angle of the Moon given equatorial coordinates.
83 *
84 * Less accurate than phaseAngleEquatorial.
85 *
86 * Arguments α, δ are geocentric right ascension and declination of the Moon;
87 * α0, δ0 are coordinates of the Sun. Angles must be in radians.
88 *
89 * @param {base.Coord} cMoon - eocentric right ascension and declination of the Moon
90 * @param {base.Coord} cSun - coordinates of the Sun
91 * @returns {number} phase angle of the Moon in radians
92 */
93function phaseAngleEquatorial2(cMoon, cSun) {
94 return Math.acos(-cosEq(cMoon.ra, cMoon.dec, cSun.ra, cSun.dec));
95}
96
97/**
98 * phaseAngleEcliptic computes the phase angle of the Moon given ecliptic coordinates.
99 *
100 * Distances must be in the same units as each other.
101 *
102 * @param {base.Coord} cMoon - geocentric longitude, latitude and distance to the Moon
103 * @param {base.Coord} cSun - longitude and distance to the Sun
104 * @returns {number} phase angle of the Moon in radians
105 */
106function phaseAngleEcliptic(cMoon, cSun) {
107 return pa(cMoon.range, cSun.range, cosEcl(cMoon.lon, cMoon.lat, cSun.lon));
108}
109
110/**
111 * cos elongation from ecliptic coordinates
112 * @private
113 */
114function cosEcl(λ, β, λ0) {
115 // (λ, β, λ0 float64) float64
116 return Math.cos(β) * Math.cos(λ - λ0);
117}
118
119/**
120 * phaseAngleEcliptic2 computes the phase angle of the Moon given ecliptic coordinates.
121 *
122 * Less accurate than phaseAngleEcliptic.
123 *
124 * Angles must be in radians.
125 *
126 * @param {base.Coord} cMoon - geocentric longitude, latitude of the Moon
127 * @param {base.Coord} cSun - longitude of the Sun
128 * @returns {number} phase angle of the Moon in radians
129 */
130function phaseAngleEcliptic2(cMoon, cSun) {
131 return Math.acos(-cosEcl(cMoon.lon, cMoon.lat, cSun.lon));
132}
133
134/**
135 * phaseAngle3 computes the phase angle of the Moon given a julian day.
136 *
137 * Less accurate than phaseAngle functions taking coordinates.
138 *
139 * Result in radians.
140 */
141function phaseAngle3(jde) {
142 // (jde float64) float64
143 var T = _base2.default.J2000Century(jde);
144 var D = _base2.default.horner(T, 297.8501921 * p, 445267.1114034 * p, -0.0018819 * p, p / 545868, -p / 113065000);
145 var m = _base2.default.horner(T, 357.5291092 * p, 35999.0502909 * p, -0.0001535 * p, p / 24490000);
146 var m_ = _base2.default.horner(T, 134.9633964 * p, 477198.8675055 * p, 0.0087414 * p, p / 69699, -p / 14712000);
147 return Math.PI - _base2.default.pmod(D, 2 * Math.PI) + -6.289 * p * Math.sin(m_) + 2.1 * p * Math.sin(m) + -1.274 * p * Math.sin(2 * D - m_) + -0.658 * p * Math.sin(2 * D) + -0.214 * p * Math.sin(2 * m_) + -0.11 * p * Math.sin(D);
148}
149
150exports.default = {
151 phaseAngleEquatorial: phaseAngleEquatorial,
152 phaseAngleEquatorial2: phaseAngleEquatorial2,
153 phaseAngleEcliptic: phaseAngleEcliptic,
154 phaseAngleEcliptic2: phaseAngleEcliptic2,
155 phaseAngle3: phaseAngle3
156};
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