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84d6aff35a
I'm starting to implement the ability to define up to 8 distinct points in the sky as "stars" that will be allowed as a `body` parameter to some Astronomy Engine functions, to be determined.
80 lines
2.7 KiB
JavaScript
80 lines
2.7 KiB
JavaScript
/*
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culminate.js - by Don Cross - 2019-06-17
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Example Node.js program for Astronomy Engine:
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https://github.com/cosinekitty/astronomy
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This example program shows how to calculate the time
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the Sun, Moon, and planets will next reach their highest point in the sky
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as seen by an observer at a given location on the Earth.
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This is called culmination, and is found by finding when
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each body's "hour angle" is 0.
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Having an hour angle of 0 is another way of saying that the body is
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crossing the meridian, the imaginary semicircle in the sky that passes
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from due north on the horizon, through the zenith (straight up),
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toward due south on the horizon. At this moment the body appears to
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have an azimuth of either 180 degrees (due south) or 0 (due north).
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To execute, run the command:
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node culminate latitude longitude [date]
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*/
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const Astronomy = require('./astronomy.js');
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function ParseNumber(text, name) {
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const x = Number(text);
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if (!Number.isFinite(x)) {
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console.error(`ERROR: Not a valid numeric value for ${name}: "${text}"`);
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process.exit(1);
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}
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return x;
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}
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function ParseDate(text) {
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const d = new Date(text);
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if (!Number.isFinite(d.getTime())) {
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console.error(`ERROR: Not a valid date: "${text}"`);
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process.exit(1);
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}
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return d;
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}
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function DisplayEvent(name, evt) {
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let text ;
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if (evt) {
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text = evt.time.date.toISOString() + ' altitude=' + evt.hor.altitude.toFixed(2).padStart(6);
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text += ' azimuth=' + evt.hor.azimuth.toFixed(2).padStart(7);
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} else {
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text = '(not found)';
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}
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console.log(name.padEnd(8) + ' : ' + text);
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}
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function Demo() {
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if (process.argv.length === 4 || process.argv.length === 5) {
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const bodylist = [
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Astronomy.Body.Sun, Astronomy.Body.Moon,
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Astronomy.Body.Mercury, Astronomy.Body.Venus, Astronomy.Body.Mars, Astronomy.Body.Jupiter,
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Astronomy.Body.Saturn, Astronomy.Body.Uranus, Astronomy.Body.Neptune, Astronomy.Body.Pluto
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];
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const latitude = ParseNumber(process.argv[2]);
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const longitude = ParseNumber(process.argv[3]);
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const observer = new Astronomy.Observer(latitude, longitude, 0);
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const date = (process.argv.length === 5) ? ParseDate(process.argv[4]) : new Date();
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console.log('search : ' + date.toISOString());
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for (let body of bodylist) {
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let culm = Astronomy.SearchHourAngle(body, observer, 0, date);
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DisplayEvent(body, culm);
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}
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process.exit(0);
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} else {
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console.log('USAGE: node culminate.js latitude longitude [date]');
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process.exit(1);
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}
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}
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Demo();
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