A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Andrés Ruiz
Date: 2010 Nov 8, 08:12 +0100
The calculation itself is simple:
GHA Aries = Sidereal Time At
JD: Julian day
T = (JD - 2451545.0 ) / 36525.0;
theta0 = 280.46061837 + 360.98564736629*(JD-2451545.0) + 0.000387933*T*T - T*T*T/38710000.0;
theta0 = ang_0_360(theta0);
GHA = theta0 + deltaPsi*COS( epsilon );
The term deltaPsi*COS( epsilon ), take account of Nutation, obliquity of the ecliptic.
And can be ignored if the accuracy of ±0.02' is not necessary
Do 0<= GHA <= 360
And of course Local Sidereal Time: LHA = GHA + L
At my Website at [Papers][ Under Development] “Astronomía de Posición” more information in english about JD and LST can be found.