119 lines
3.3 KiB
JavaScript
119 lines
3.3 KiB
JavaScript
'use strict';
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Object.defineProperty(exports, '__esModule', { value: true });
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var sexagesimal = require('./sexagesimal.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 refraction
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*/
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const { sin, tan } = Math;
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const D2R = Math.PI / 180;
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const gt15true1 = new sexagesimal["default"].Angle(false, 0, 0, 58.294).rad();
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const gt15true2 = new sexagesimal["default"].Angle(false, 0, 0, 0.0668).rad();
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const gt15app1 = new sexagesimal["default"].Angle(false, 0, 0, 58.276).rad();
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const gt15app2 = new sexagesimal["default"].Angle(false, 0, 0, 0.0824).rad();
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/**
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* gt15True returns refraction for obtaining true altitude when altitude
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* is greater than 15 degrees (about 0.26 radians.)
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*
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* h0 must be a measured apparent altitude of a celestial body in radians.
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*
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* Result is refraction to be subtracted from h0 to obtain the true altitude
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* of the body. Unit is radians.
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*/
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function gt15True (h0) { // (h0 float64) float64
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// (16.1) p. 105
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const t = tan(Math.PI / 2 - h0);
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return gt15true1 * t - gt15true2 * t * t * t
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}
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/**
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* gt15Apparent returns refraction for obtaining apparent altitude when
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* altitude is greater than 15 degrees (about 0.26 radians.)
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*
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* h must be a computed true "airless" altitude of a celestial body in radians.
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*
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* Result is refraction to be added to h to obtain the apparent altitude
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* of the body. Unit is radians.
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*/
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function gt15Apparent (h) { // (h float64) float64
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// (16.2) p. 105
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const t = tan(Math.PI / 2 - h);
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return gt15app1 * t - gt15app2 * t * t * t
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}
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/**
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* Bennett returns refraction for obtaining true altitude.
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*
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* h0 must be a measured apparent altitude of a celestial body in radians.
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*
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* Results are accurate to 0.07 arc min from horizon to zenith.
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*
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* Result is refraction to be subtracted from h0 to obtain the true altitude
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* of the body. Unit is radians.
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*/
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function bennett (h0) { // (h0 float64) float64
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// (16.3) p. 106
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const c1 = D2R / 60;
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const c731 = 7.31 * D2R * D2R;
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const c44 = 4.4 * D2R;
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return c1 / tan(h0 + c731 / (h0 + c44))
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}
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/**
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* Bennett2 returns refraction for obtaining true altitude.
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*
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* Similar to Bennett, but a correction is applied to give a more accurate
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* result.
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*
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* Results are accurate to 0.015 arc min. Result unit is radians.
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*/
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function bennett2 (h0) { // (h0 float64) float64
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const cMin = 60 / D2R;
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const c06 = 0.06 / cMin;
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const c147 = 14.7 * cMin * D2R;
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const c13 = 13 * D2R;
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const R = bennett(h0);
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return R - c06 * sin(c147 * R + c13)
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}
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/**
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* Saemundsson returns refraction for obtaining apparent altitude.
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*
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* h must be a computed true "airless" altitude of a celestial body in radians.
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*
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* Result is refraction to be added to h to obtain the apparent altitude
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* of the body.
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*
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* Results are consistent with Bennett to within 4 arc sec.
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* Result unit is radians.
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*/
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function saemundsson (h) { // (h float64) float64
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// (16.4) p. 106
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const c102 = 1.02 * D2R / 60;
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const c103 = 10.3 * D2R * D2R;
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const c511 = 5.11 * D2R;
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return c102 / tan(h + c103 / (h + c511))
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}
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var refraction = {
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gt15True,
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gt15Apparent,
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bennett,
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bennett2,
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saemundsson
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};
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exports.bennett = bennett;
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exports.bennett2 = bennett2;
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exports["default"] = refraction;
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exports.gt15Apparent = gt15Apparent;
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exports.gt15True = gt15True;
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exports.saemundsson = saemundsson;
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