Add the E-terms (elliptic component of annual aberration) to a
pre IAU 1976 mean place to conform to the old catalogue convention.
CALL sla_ADDET (RM, DM, EQ, RC, DC)
without E-terms (radians)
Besselian epoch of mean equator and equinox
with E-terms included (radians)
Most star positions from pre-1984 optical catalogues (or
obtained by astrometry with respect to such stars) have the
E-terms built-in. If it is necessary to convert a formal mean
place (for example a pulsar timing position) to one
consistent with such a star catalogue, then the
should be adjusted using this routine.
Explanatory Supplement to the Astronomical Ephemeris,
section 2D, page 48.