From b0cb2767577a654db082f5ae9bbd69ffde725d2e Mon Sep 17 00:00:00 2001
From: "David A. Madore" <david+git@madore.org>
Date: Tue, 27 Mar 2012 19:23:09 +0200
Subject: Equation of the origins/equinoxes.

---
 org/madore/ephem/Nutation.java   | 10 +++++++++-
 org/madore/ephem/Precession.java |  2 ++
 org/madore/ephem/nutation.dat    | 34 ++++++++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+), 1 deletion(-)

(limited to 'org')

diff --git a/org/madore/ephem/Nutation.java b/org/madore/ephem/Nutation.java
index ecc08a4..dcfdc30 100644
--- a/org/madore/ephem/Nutation.java
+++ b/org/madore/ephem/Nutation.java
@@ -10,7 +10,7 @@ import java.io.BufferedReader;
 public final class Nutation {
 
     public static enum Variable {
-	PSI("psi"), EPSILON("epsilon");
+	PSI("psi"), EPSILON("epsilon"), EQORG("eqorg");
 	final String name;
 	Variable(String name) { this.name = name; }
     }
@@ -70,4 +70,12 @@ public final class Nutation {
 	return mat3;
     }
 
+    public static double eqeqnx(double t) { // Equation of the equinoxes (=GAST-GMST, in arc seconds)
+	return getFunc(Variable.PSI).v(t)*Math.cos(Precession.epsilon.v(t)) + getFunc(Variable.EQORG).v(t);
+    }
+
+    public static double eqorg(double t) {
+	return Precession.eqorg.v(t) + eqeqnx(t);
+    }
+
 }
diff --git a/org/madore/ephem/Precession.java b/org/madore/ephem/Precession.java
index b52a1c5..8b556d5 100644
--- a/org/madore/ephem/Precession.java
+++ b/org/madore/ephem/Precession.java
@@ -12,6 +12,8 @@ public final class Precession {
 	= new Comput.Polynomial(0, 10.556403, -2.3814292, -0.00121197, 0.000170663, -0.0000000560);
     public static Comput.Polynomial epsilon
 	= new Comput.Polynomial(epsilon0, -46.836769, -0.0001831, 0.00200340, -0.000000576, -0.0000000434);
+    public static Comput.Polynomial eqorg
+	= new Comput.Polynomial(0.014506, 4612.156534, 1.3915817, -0.00000044, -0.000029956, -0.0000000368);
 
     public static Frames.RotationMatrix matrix(double t) {
 	Frames.RotationMatrix mat1 = Frames.RotationMatrix.rotx(epsilon0*Comput.arcsecond);
diff --git a/org/madore/ephem/nutation.dat b/org/madore/ephem/nutation.dat
index a685e1f..efc785c 100644
--- a/org/madore/ephem/nutation.dat
+++ b/org/madore/ephem/nutation.dat
@@ -2412,3 +2412,37 @@ nutation	epsilon	1	1,0,2,-2,2,0,0,0,0,0,0,0,0,0	0.00000000	0.00000100
 nutation	epsilon	1	0,0,2,-2,1,0,0,0,0,0,0,0,0,0	0.00000000	-0.00000090
 nutation	epsilon	1	0,1,0,0,1,0,0,0,0,0,0,0,0,0	0.00000000	-0.00000020
 nutation	epsilon	1	0,2,0,0,0,0,0,0,0,0,0,0,0,0	0.00000000	-0.00000010
+nutation	eqorg	0	0,0,0,0,1,0,0,0,0,0,0,0,0,0	0.00264096	-0.00000039
+nutation	eqorg	0	0,0,0,0,2,0,0,0,0,0,0,0,0,0	0.00006352	-0.00000002
+nutation	eqorg	0	0,0,2,-2,3,0,0,0,0,0,0,0,0,0	0.00001175	0.00000001
+nutation	eqorg	0	0,0,2,-2,1,0,0,0,0,0,0,0,0,0	0.00001121	0.00000001
+nutation	eqorg	0	0,0,2,-2,2,0,0,0,0,0,0,0,0,0	-0.00000455	0.00000000
+nutation	eqorg	0	0,0,2,0,3,0,0,0,0,0,0,0,0,0	0.00000202	0.00000000
+nutation	eqorg	0	0,0,2,0,1,0,0,0,0,0,0,0,0,0	0.00000198	0.00000000
+nutation	eqorg	0	0,0,0,0,3,0,0,0,0,0,0,0,0,0	-0.00000172	0.00000000
+nutation	eqorg	0	0,1,0,0,1,0,0,0,0,0,0,0,0,0	-0.00000141	-0.00000001
+nutation	eqorg	0	0,1,0,0,-1,0,0,0,0,0,0,0,0,0	-0.00000126	-0.00000001
+nutation	eqorg	0	1,0,0,0,-1,0,0,0,0,0,0,0,0,0	-0.00000063	0.00000000
+nutation	eqorg	0	1,0,0,0,1,0,0,0,0,0,0,0,0,0	-0.00000063	0.00000000
+nutation	eqorg	0	0,1,2,-2,3,0,0,0,0,0,0,0,0,0	0.00000046	0.00000000
+nutation	eqorg	0	0,1,2,-2,1,0,0,0,0,0,0,0,0,0	0.00000045	0.00000000
+nutation	eqorg	0	0,0,4,-4,4,0,0,0,0,0,0,0,0,0	0.00000036	0.00000000
+nutation	eqorg	0	0,0,1,-1,1,0,-8,12,0,0,0,0,0,0	-0.00000024	-0.00000012
+nutation	eqorg	0	0,0,2,0,0,0,0,0,0,0,0,0,0,0	0.00000032	0.00000000
+nutation	eqorg	0	0,0,2,0,2,0,0,0,0,0,0,0,0,0	0.00000028	0.00000000
+nutation	eqorg	0	1,0,2,0,3,0,0,0,0,0,0,0,0,0	0.00000027	0.00000000
+nutation	eqorg	0	1,0,2,0,1,0,0,0,0,0,0,0,0,0	0.00000026	0.00000000
+nutation	eqorg	0	0,0,2,-2,0,0,0,0,0,0,0,0,0,0	-0.00000021	0.00000000
+nutation	eqorg	0	0,1,-2,2,-3,0,0,0,0,0,0,0,0,0	0.00000019	0.00000000
+nutation	eqorg	0	0,1,-2,2,-1,0,0,0,0,0,0,0,0,0	0.00000018	0.00000000
+nutation	eqorg	0	0,0,0,0,0,0,8,-13,0,0,0,0,0,-1	-0.00000010	0.00000005
+nutation	eqorg	0	0,0,0,2,0,0,0,0,0,0,0,0,0,0	0.00000015	0.00000000
+nutation	eqorg	0	2,0,-2,0,-1,0,0,0,0,0,0,0,0,0	-0.00000014	0.00000000
+nutation	eqorg	0	1,0,0,-2,1,0,0,0,0,0,0,0,0,0	0.00000014	0.00000000
+nutation	eqorg	0	0,1,2,-2,2,0,0,0,0,0,0,0,0,0	-0.00000014	0.00000000
+nutation	eqorg	0	1,0,0,-2,-1,0,0,0,0,0,0,0,0,0	0.00000014	0.00000000
+nutation	eqorg	0	0,0,4,-2,4,0,0,0,0,0,0,0,0,0	0.00000013	0.00000000
+nutation	eqorg	0	0,0,2,-2,4,0,0,0,0,0,0,0,0,0	-0.00000011	0.00000000
+nutation	eqorg	0	1,0,-2,0,-3,0,0,0,0,0,0,0,0,0	0.00000011	0.00000000
+nutation	eqorg	0	1,0,-2,0,-1,0,0,0,0,0,0,0,0,0	0.00000011	0.00000000
+nutation	eqorg	1	0,0,0,0,1,0,0,0,0,0,0,0,0,0	-0.00000087	0.00000000
-- 
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