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Diffstat (limited to 'src/slalib/eqeqx.f')
| -rw-r--r-- | src/slalib/eqeqx.f | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/src/slalib/eqeqx.f b/src/slalib/eqeqx.f new file mode 100644 index 0000000..f811039 --- /dev/null +++ b/src/slalib/eqeqx.f @@ -0,0 +1,57 @@ + DOUBLE PRECISION FUNCTION sla_EQEQX (DATE) +*+ +* - - - - - - +* E Q E Q 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 + sla_EQEQX +* +* References: IAU Resolution C7, Recommendation 3 (1994) +* Capitaine, N. & Gontier, A.-M., Astron. Astrophys., +* 275, 645-650 (1993) +* +* Called: sla_NUTC +* +* Patrick Wallace Starlink 23 August 1996 +* +* Copyright (C) 1996 Rutherford Appleton Laboratory +*- + + 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 sla_NUTC(DATE,DPSI,DEPS,EPS0) + +* Equation of the equinoxes + sla_EQEQX=DPSI*COS(EPS0)+AS2R*(0.00264D0*SIN(OM)+ + : 0.000063D0*SIN(OM+OM)) + + END |