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DOUBLE PRECISION FUNCTION slEQEX (DATE)
*+
* - - - - - -
* E Q E X
* - - - - - -
*
* Equation of the equinoxes (IAU 1994, double precision)
*
* Given:
* DATE dp TDB (loosely ET) as Modified Julian Date
* (JD-2400000.5)
*
* The result is the equation of the equinoxes (double precision)
* in radians:
*
* Greenwich apparent ST = GMST + slEQEX
*
* References: IAU Resolution C7, Recommendation 3 (1994)
* Capitaine, N. & Gontier, A.-M., Astron. Astrophys.,
* 275, 645-650 (1993)
*
* Called: slNUTC
*
* Patrick Wallace Starlink 23 August 1996
*
* Copyright (C) 1996 Rutherford Appleton Laboratory
*
* License:
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program (see SLA_CONDITIONS); if not, write to the
* Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301 USA
*
* Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
*-
IMPLICIT NONE
DOUBLE PRECISION DATE
* Turns to arc seconds and arc seconds to radians
DOUBLE PRECISION T2AS,AS2R
PARAMETER (T2AS=1296000D0,
: AS2R=0.484813681109535994D-5)
DOUBLE PRECISION T,OM,DPSI,DEPS,EPS0
* Interval between basic epoch J2000.0 and current epoch (JC)
T=(DATE-51544.5D0)/36525D0
* Longitude of the mean ascending node of the lunar orbit on the
* ecliptic, measured from the mean equinox of date
OM=AS2R*(450160.280D0+(-5D0*T2AS-482890.539D0
: +(7.455D0+0.008D0*T)*T)*T)
* Nutation
CALL slNUTC(DATE,DPSI,DEPS,EPS0)
* Equation of the equinoxes
slEQEX=DPSI*COS(EPS0)+AS2R*(0.00264D0*SIN(OM)+
: 0.000063D0*SIN(OM+OM))
END
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