practical-astronomy-javascript
v1.0.0
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Implementation of algorithms from Practical Astronomy For Your Calculator or Spreadsheet
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Practical Astronomy - JavaScript (practical-astronomy-javascript)
Algorithms from "Practical Astronomy with your Calculator or Spreadsheet" by Peter Duffett-Smith, implemented in JavaScript.
If you're interested in this topic, please buy the book! It provides far more detail and context.
Installation
npm install practical-astronomy-javascript
Usage
Example 1: Calculate date of Easter for 2024.
Create client.js:
const pa = require('practical-astronomy-javascript');
console.log(pa.paDateTime.getDateOfEaster(2024));
Run it:
node client.js
Result:
[ 3, 31, 2024 ]
Example 2: Get detailed information about the April 8 solar eclipse, for West Alexandria, Ohio
Create client.js:
const pa = require('practical-astronomy-javascript');
// Information about the observer location
var monthOfObservation = 4;
var dayOfObservation = 8;
var yearOfObservation = 2024;
var isDaylightSavings = true;
var zoneCorrectionHours = 5;
var observerLatitude = 39.74722;
var observerLongitude = -84.53639;
var [solarEclipseCertainDateDay, solarEclipseCertainDateMonth, solarEclipseCertainDateYear, utFirstContactHour, utFirstContactMinutes, utMidEclipseHour, utMidEclipseMinutes, utLastContactHour, utLastContactMinutes, eclipseMagnitude] = pa.paEclipses.solarEclipseCircumstances(dayOfObservation, monthOfObservation, yearOfObservation, isDaylightSavings, zoneCorrectionHours, observerLongitude, observerLatitude);
// Results are in universal time, so adjust them for the observer's time zone
utFirstContactHour = utFirstContactHour - ((isDaylightSavings) ? zoneCorrectionHours - 1 : zoneCorrectionHours);
utMidEclipseHour = utMidEclipseHour - ((isDaylightSavings) ? zoneCorrectionHours - 1 : zoneCorrectionHours);
utLastContactHour = utLastContactHour - ((isDaylightSavings) ? zoneCorrectionHours - 1 : zoneCorrectionHours);
console.log(`Date of eclipse: ${solarEclipseCertainDateMonth}/${solarEclipseCertainDateDay}/${solarEclipseCertainDateYear}`);
console.log(`First contact: ${utFirstContactHour}:${utFirstContactMinutes}`);
console.log(`Mid-eclipse (totality): ${utMidEclipseHour}:${utMidEclipseMinutes}`);
console.log(`Last contact: ${utLastContactHour}:${utLastContactMinutes}`);
console.log(`Magnitude of eclipse: ${eclipseMagnitude}`);
Run it:
node client.js
Result:
Date of eclipse: 4/8/2024
First contact: 13:55
Mid-eclipse (totality): 15:11
Last contact: 16:27
Magnitude of eclipse: 1.006
Links
Library Functions - Status
Date/Time
- [x] Calculate -> Date of Easter
- [x] Convert -> Civil Date to Day Number
- [x] Convert -> Civil Time <-> Decimal Hours
- [x] Extract -> Hour, Minutes, and Seconds parts of Decimal Hours
- [x] Convert -> Local Civil Time <-> Universal Time
- [x] Convert -> Universal Time <-> Greenwich Sidereal Time
- [x] Convert -> Greenwich Sidereal Time <-> Local Sidereal Time
Coordinates
- [x] Convert -> Angle <-> Decimal Degrees
- [x] Convert -> Right Ascension <-> Hour Angle
- [x] Convert -> Equatorial Coordinates <-> Horizon Coordinates
- [x] Calculate -> Obliquity of the Ecliptic
- [x] Convert -> Ecliptic Coordinates <-> Equatorial Coordinates
- [x] Convert -> Equatorial Coordinates <-> Galactic Coordinates
- [x] Calculate -> Angle between two objects
- [x] Calculate -> Rising and Setting times for an object
- [x] Calculate -> Precession (corrected coordinates between two epochs)
- [x] Calculate -> Nutation (in ecliptic longitude and obliquity) for a Greenwich date
- [x] Calculate -> Effects of aberration for ecliptic coordinates
- [x] Calculate -> RA and Declination values, corrected for atmospheric refraction
- [x] Calculate -> RA and Declination values, corrected for geocentric parallax
- [x] Calculate -> Heliographic coordinates
- [x] Calculate -> Carrington rotation number
- [x] Calculate -> Selenographic (lunar) coordinates (sub-Earth and sub-Solar)
The Sun
- [x] Calculate -> Approximate and precise positions of the Sun
- [x] Calculate -> Sun's distance and angular size
- [x] Calculate -> Local sunrise and sunset
- [x] Calculate -> Morning and evening twilight
- [x] Calculate -> Equation of time
- [x] Calculate -> Solar elongation
Planets
- [x] Calculate -> Approximate position of planet
- [x] Calculate -> Precise position of planet
- [x] Calculate -> Visual aspects of planet (distance, angular diameter, phase, light time, position angle of bright limb, and apparent magnitude)
Comets
- [x] Calculate -> Position of comet (elliptical)
- [x] Calculate -> Position of comet (parabolic)
Binary Stars
- [x] Calculate -> Binary star orbit data
The Moon
- [x] Calculate -> Approximate and precise position of Moon
- [x] Calculate -> Moon phase and position angle of bright limb
- [x] Calculate -> Times of new Moon and full Moon
- [x] Calculate -> Moon's distance, angular diameter, and horizontal parallax
- [x] Calculate -> Local moonrise and moonset
Eclipses
- [x] Calculate -> Lunar eclipse occurrence and circumstances
- [x] Calculate -> Solar eclipse occurrence and circumstances