
ACTION:
 Equation of the equinoxes (IAU 1994).

CALL:
D = sla_EQEQX (DATE)
GIVEN:
DATE  D  TDB (formerly ET) as Modified Julian Date
(JD$$2400000.5) 

RETURNED:
sla_EQEQX  D  The equation of the equinoxes (radians) 


NOTES:


(1)
 The equation of the equinoxes is defined here as GAST $$ GMST:
it is added to a mean sidereal time to give the apparent sidereal time.

(2)
 The change from the classic “textbook” expression $\Delta \psi \phantom{\rule{0.3em}{0ex}}cos\phantom{\rule{0.3em}{0ex}}\u03f5$
occurred with IAU Resolution C7, Recommendation 3 (1994). The new formulation
takes into account crossterms between the various precession and nutation quantities,
amounting to about 3 milliarcsec. The transition from the old to the new model
officially took place on 1997 February 27.

REFERENCE:
 Capitaine, N. & Gontier, A.M. (1993), Astron. Astrophys., 275, 645650.