Practical Astronomy : Menghitung Julian Day

Berikut adalah seri postingan tentang astronomi praktis. Seri ini memiliki tujuan akhir yaitu membuat class Java yang berisi perhitungan-perhitungan dari buku Practical Astronomy with your calculator or spreadsheet 4th Edition by Peter Duffett and Jonathan Zwart.

Kali ini menghitung Julian Day dari kalender gregorian day.

	public class ShowJulianDay
	{
	// arguments are passed using the text field below this editor
	public static void main(String[] args)
	{
	PracticalAstronomy astro = new PracticalAstronomy(2009,6,19,18,0,0);
	System.out.print(astro.getJulianDay());
	}
	}
	public class PracticalAstronomy
	{
	private int year;
	private int month;
	private int day;
	private int hour;
	private int minute;
	private int second;
	public PracticalAstronomy(int year,int month,int day,int hour,int minute,int second)
	{
	this.year = year;
	this.month = month;
	this.day = day;
	this.hour = hour;
	this.minute = minute;
	this.second = second;
	}
	public double getJulianDay()
	{
	boolean julian = true;
	if (year < 1582 || (year == 1582 && month <= 10) || (year == 1582 && month == 10 && day < 15)) julian = false;
	int D = day;
	int M = month;
	int Y = year;
	if (M < 3)
	{
	Y--;
	M += 12;
	}
	int A = Y / 100;
	int B = julian ? 2 - A + A / 4 : 0;
	int C = Y < 0 ? (int)((365.25 * Y) - 0.75) : (int)(365.25 * Y);
	int F = (int)(30.6001 * (M + 1));
	double dayFraction = (hour + (minute + (second / 60.0)) / 60.0) / 24.0;
	double jd = B + C + F + D + dayFraction + 1720994.5;
	return jd;
	}
	}

view raw PracticalAstronomy_GDtoJD.java hosted with by GitHub

Untuk testing code diatas bisa menggunakan java compiler dan executor disini https://www.compilejava.net/