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Diffstat (limited to 'src/slalib/subet.f')
-rw-r--r-- | src/slalib/subet.f | 66 |
1 files changed, 66 insertions, 0 deletions
diff --git a/src/slalib/subet.f b/src/slalib/subet.f new file mode 100644 index 0000000..e36575b --- /dev/null +++ b/src/slalib/subet.f @@ -0,0 +1,66 @@ + SUBROUTINE sla_SUBET (RC, DC, EQ, RM, DM) +*+ +* - - - - - - +* S U B E T +* - - - - - - +* +* Remove the E-terms (elliptic component of annual aberration) +* from a pre IAU 1976 catalogue RA,Dec to give a mean place +* (double precision) +* +* Given: +* RC,DC dp RA,Dec (radians) with E-terms included +* EQ dp Besselian epoch of mean equator and equinox +* +* Returned: +* RM,DM dp RA,Dec (radians) without E-terms +* +* Called: +* sla_ETRMS, sla_DCS2C, sla_,DVDV, sla_DCC2S, sla_DRANRM +* +* Explanation: +* Most star positions from pre-1984 optical catalogues (or +* derived from astrometry using such stars) embody the +* E-terms. This routine converts such a position to a +* formal mean place (allowing, for example, comparison with a +* pulsar timing position). +* +* Reference: +* Explanatory Supplement to the Astronomical Ephemeris, +* section 2D, page 48. +* +* P.T.Wallace Starlink 10 May 1990 +* +* Copyright (C) 1995 Rutherford Appleton Laboratory +*- + + IMPLICIT NONE + + DOUBLE PRECISION RC,DC,EQ,RM,DM + + DOUBLE PRECISION sla_DRANRM,sla_DVDV + DOUBLE PRECISION A(3),V(3),F + + INTEGER I + + + +* E-terms + CALL sla_ETRMS(EQ,A) + +* Spherical to Cartesian + CALL sla_DCS2C(RC,DC,V) + +* Include the E-terms + F=1D0+sla_DVDV(V,A) + DO I=1,3 + V(I)=F*V(I)-A(I) + END DO + +* Cartesian to spherical + CALL sla_DCC2S(V,RM,DM) + +* Bring RA into conventional range + RM=sla_DRANRM(RM) + + END |