From 5f00eb3230d89f98d93c6e5bc8ecfa72e4e89b07 Mon Sep 17 00:00:00 2001 From: "David A. Madore" Date: Tue, 17 Apr 2012 19:15:56 +0200 Subject: Use J2000 ecliptic (rather than equatorial) coordinates as starting point for precession. We will assume that these are the coordinates returned by VSOP87. --- org/madore/ephem/Nutation.java | 1 + 1 file changed, 1 insertion(+) (limited to 'org/madore/ephem/Nutation.java') diff --git a/org/madore/ephem/Nutation.java b/org/madore/ephem/Nutation.java index bc6e721..8c37fd2 100644 --- a/org/madore/ephem/Nutation.java +++ b/org/madore/ephem/Nutation.java @@ -64,6 +64,7 @@ public final class Nutation { } public static Frames.Rotation matrix(double t) { + // Transform mean equatorial coordinates of date to true equatorial coordinates of date. Frames.Rotation mat1 = Frames.Rotation.rotx(Precession.epsilon.v(t)*Comput.arcsecond); Frames.Rotation mat2 = Frames.Rotation.rotz(-getFunc(Variable.PSI).v(t)*Comput.arcsecond).apply(mat1); Frames.Rotation mat3 = Frames.Rotation.rotx(-(Precession.epsilon.v(t)+getFunc(Variable.EPSILON).v(t))*Comput.arcsecond).apply(mat2); -- cgit v1.2.3