Remove the E-terms (elliptic component of annual aberration)
from a pre IAU 1976 catalogue to give a mean place.
CALL sla_SUBET (RC, DC, EQ, RM, DM)
with E-terms included (radians)
Besselian epoch of mean equator and equinox
without E-terms (radians)
Most star positions from pre-1984 optical catalogues (or
obtained by astrometry with respect to such stars) have the
E-terms built-in. This routine converts such a position to a
formal mean place (allowing, for example, comparison with a
pulsar timing position).
Explanatory Supplement to the Astronomical Ephemeris,
section 2D, page 48.