75 lines
2.1 KiB
JavaScript
75 lines
2.1 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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var nutation = require('./nutation.cjs');
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var solar = require('./solar.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 solardisk
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*/
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/**
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* Ephemeris returns the apparent orientation of the sun at the given jd.
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*
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* Results:
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* P: Position angle of the solar north pole.
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* B0: Heliographic latitude of the center of the solar disk.
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* L0: Heliographic longitude of the center of the solar disk.
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*
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* All results in radians.
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*/
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function ephemeris (jd, earth) { // (jd float64, e *pp.V87Planet) (P, B0, L0 float64)
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const θ = (jd - 2398220) * 2 * Math.PI / 25.38;
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const I = 7.25 * Math.PI / 180;
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const K = 73.6667 * Math.PI / 180 +
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1.3958333 * Math.PI / 180 * (jd - 2396758) / base["default"].JulianCentury;
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const solarPos = solar["default"].trueVSOP87(earth, jd);
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const L = solarPos.lon;
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const R = solarPos.range;
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const [Δψ, Δε] = nutation["default"].nutation(jd);
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const ε0 = nutation["default"].meanObliquity(jd);
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const ε = ε0 + Δε;
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const λ = L - 20.4898 / 3600 * Math.PI / 180 / R;
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const λp = λ + Δψ;
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const [sλK, cλK] = base["default"].sincos(λ - K);
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const [sI, cI] = base["default"].sincos(I);
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const tx = -Math.cos(λp) * Math.tan(ε);
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const ty = -cλK * Math.tan(I);
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const P = Math.atan(tx) + Math.atan(ty);
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const B0 = Math.asin(sλK * sI);
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const η = Math.atan2(-sλK * cI, -cλK);
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const L0 = base["default"].pmod(η - θ, 2 * Math.PI);
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return [P, B0, L0]
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}
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/**
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* Cycle returns the jd of the start of the given synodic rotation.
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*
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* Argument c is the "Carrington" cycle number.
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*
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* Result is a dynamical time (not UT).
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*/
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function cycle (c) { // (c int) (jde float64)
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const jde = 2398140.227 + 27.2752316 * c;
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const m = 281.96 * Math.PI / 180 + 26.882476 * Math.PI / 180 * c;
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const [s2m, c2m] = base["default"].sincos(2 * m);
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return jde + 0.1454 * Math.sin(m) - 0.0085 * s2m - 0.0141 * c2m
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}
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var solardisk = {
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ephemeris,
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cycle
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};
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exports.cycle = cycle;
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exports["default"] = solardisk;
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exports.ephemeris = ephemeris;
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