adhan-extended/lib/esm/SolarTime.js

High precision Islamic prayer time library (extended)

import Astronomical from './Astronomical';
import { degreesToRadians, radiansToDegrees } from './MathUtils';
import SolarCoordinates from './SolarCoordinates';
export default class SolarTime {
  constructor(date, coordinates) {
    const julianDay = Astronomical.julianDay(date.getFullYear(), date.getMonth() + 1, date.getDate(), 0);
    this.observer = coordinates;
    this.solar = new SolarCoordinates(julianDay);
    this.prevSolar = new SolarCoordinates(julianDay - 1);
    this.nextSolar = new SolarCoordinates(julianDay + 1);
    const m0 = Astronomical.approximateTransit(coordinates.longitude, this.solar.apparentSiderealTime, this.solar.rightAscension);
    const solarAltitude = -50.0 / 60.0;
    this.approxTransit = m0;
    this.transit = Astronomical.correctedTransit(m0, coordinates.longitude, this.solar.apparentSiderealTime, this.solar.rightAscension, this.prevSolar.rightAscension, this.nextSolar.rightAscension);
    this.sunrise = Astronomical.correctedHourAngle(m0, solarAltitude, coordinates, false, this.solar.apparentSiderealTime, this.solar.rightAscension, this.prevSolar.rightAscension, this.nextSolar.rightAscension, this.solar.declination, this.prevSolar.declination, this.nextSolar.declination);
    this.sunset = Astronomical.correctedHourAngle(m0, solarAltitude, coordinates, true, this.solar.apparentSiderealTime, this.solar.rightAscension, this.prevSolar.rightAscension, this.nextSolar.rightAscension, this.solar.declination, this.prevSolar.declination, this.nextSolar.declination);
  }

  hourAngle(angle, afterTransit) {
    return Astronomical.correctedHourAngle(this.approxTransit, angle, this.observer, afterTransit, this.solar.apparentSiderealTime, this.solar.rightAscension, this.prevSolar.rightAscension, this.nextSolar.rightAscension, this.solar.declination, this.prevSolar.declination, this.nextSolar.declination);
  }

  afternoon(shadowLength) {
    // TODO source shadow angle calculation
    const tangent = Math.abs(this.observer.latitude - this.solar.declination);
    const inverse = shadowLength + Math.tan(degreesToRadians(tangent));
    const angle = radiansToDegrees(Math.atan(1.0 / inverse));
    return this.hourAngle(angle, true);
  }

}
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