94 lines
2.9 KiB
JavaScript
94 lines
2.9 KiB
JavaScript
'use strict';
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Object.defineProperty(exports, '__esModule', { value: true });
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var interpolation = require('./interpolation.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 conjunction
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*/
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/**
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* Planetary computes a conjunction between two moving objects, such as planets.
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*
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* Conjunction is found with interpolation against length 5 ephemerides.
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*
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* t1, t5 are times of first and last rows of ephemerides. The scale is
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* arbitrary.
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*
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* cs1 is the ephemeris of the first object. The columns may be celestial
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* coordinates in right ascension and declination or ecliptic coordinates in
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* longitude and latitude.
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*
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* cs2 is the ephemeris of the second object, in the same frame as the first.
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*
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* Return value t is time of conjunction in the scale of t1, t5.
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*
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* @param {Number} t1 - julian ephemeris day of first row
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* @param {Number} t5 - julian ephemeris day of fifth row
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* @param {Coord[]} cs1 - ephemeris of first moving object
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* @param {Coord[]} cs2 - ephemeris of decond moving object
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* @return {Array}
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* {Number} t - time of conjunction in JDE
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* {Number} Δd - is the amount that object 2 was "above" object 1 at the time of conjunction.
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*/
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function planetary (t1, t5, cs1, cs2) {
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if (cs1.length !== 5 || cs2.length !== 5) {
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throw new Error('Five rows required in ephemerides')
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}
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const dr = new Array(5);
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const dd = new Array(5);
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cs1.forEach((r, i) => {
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dr[i] = cs2[i].ra - cs1[i].ra;
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dd[i] = cs2[i].dec - cs1[i].dec;
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});
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return conj(t1, t5, dr, dd)
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}
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/**
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* Stellar computes a conjunction between a moving and non-moving object.
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*
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* Arguments and return values same as with Planetary, except the non-moving
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* object is c1. The ephemeris of the moving object is cs2.
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*
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* @param {Number} t1 - julian ephemeris day of first row
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* @param {Number} t5 - julian ephemeris day of fifth row
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* @param {Coord} c1 - ephemeris of non-moving object
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* @param {Coord[]} cs2 - ephemeris of moving object
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* @return {Array}
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* {Number} t - time of conjunction in JDE
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* {Number} Δd - is the amount that object 2 was "above" object 1 at the time of conjunction.
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*/
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function stellar (t1, t5, c1, cs2) {
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if (cs2.length !== 5) {
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throw new Error('Five rows required in ephemerides')
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}
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const dr = new Array(5);
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const dd = new Array(5);
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cs2.forEach((r, i) => {
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dr[i] = cs2[i].ra - c1.ra;
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dd[i] = cs2[i].dec - c1.dec;
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});
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return conj(t1, t5, dr, dd)
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}
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const conj = function (t1, t5, dr, dd) { // (t1, t5 float64, dr, dd []float64) (t, Δd float64, err error)
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let l5 = new interpolation["default"].Len5(t1, t5, dr);
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const t = l5.zero(true);
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l5 = new interpolation["default"].Len5(t1, t5, dd);
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const Δd = l5.interpolateXStrict(t);
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return [t, Δd]
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};
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var conjunction = {
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planetary,
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stellar
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};
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exports["default"] = conjunction;
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exports.planetary = planetary;
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exports.stellar = stellar;
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