From d54fe7c1f704a63824c5bfa0ece65245572e9b27 Mon Sep 17 00:00:00 2001
From: Joseph Hunkeler <jhunkeler@gmail.com>
Date: Wed, 4 Mar 2015 21:21:30 -0500
Subject: Initial commit

---
 src/slalib/ecmat.f | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 src/slalib/ecmat.f

(limited to 'src/slalib/ecmat.f')

diff --git a/src/slalib/ecmat.f b/src/slalib/ecmat.f
new file mode 100644
index 0000000..3a1f8d4
--- /dev/null
+++ b/src/slalib/ecmat.f
@@ -0,0 +1,52 @@
+      SUBROUTINE sla_ECMAT (DATE, RMAT)
+*+
+*     - - - - - -
+*      E C M A T
+*     - - - - - -
+*
+*  Form the equatorial to ecliptic rotation matrix - IAU 1980 theory
+*  (double precision)
+*
+*  Given:
+*     DATE     dp         TDB (loosely ET) as Modified Julian Date
+*                                            (JD-2400000.5)
+*  Returned:
+*     RMAT     dp(3,3)    matrix
+*
+*  Reference:
+*     Murray,C.A., Vectorial Astrometry, section 4.3.
+*
+*  Note:
+*    The matrix is in the sense   V(ecl)  =  RMAT * V(equ);  the
+*    equator, equinox and ecliptic are mean of date.
+*
+*  Called:  sla_DEULER
+*
+*  P.T.Wallace   Starlink   23 August 1996
+*
+*  Copyright (C) 1996 Rutherford Appleton Laboratory
+*-
+
+      IMPLICIT NONE
+
+      DOUBLE PRECISION DATE,RMAT(3,3)
+
+*  Arc seconds to radians
+      DOUBLE PRECISION AS2R
+      PARAMETER (AS2R=0.484813681109535994D-5)
+
+      DOUBLE PRECISION T,EPS0
+
+
+
+*  Interval between basic epoch J2000.0 and current epoch (JC)
+      T = (DATE-51544.5D0)/36525D0
+
+*  Mean obliquity
+      EPS0 = AS2R*
+     :   (84381.448D0+(-46.8150D0+(-0.00059D0+0.001813D0*T)*T)*T)
+
+*  Matrix
+      CALL sla_DEULER('X',EPS0,0D0,0D0,RMAT)
+
+      END
-- 
cgit