SLA_EQEQX - Equation of the Equinoxes   

ACTION:

Equation of the equinoxes (IAU 1994).

CALL:

D = sla_EQEQX (DATE)

GIVEN:

DATE TDB (formerly ET) as Modified Julian Date (JD-2400000.5)

RETURNED:

sla_EQEQX 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 $\Delta\psi\,cos\,\epsilon$ occurred with IAU Resolution C7, Recommendation 3 (1994). The new formulation takes into account cross-terms between the various precession and nutation quantities, amounting to about 3 milliarcsec. The transition from the old to the new model officially takes place on 1997 February 27.

REFERENCE:

Capitaine, N. & Gontier, A.-M. (1993), Astron. Astrophys., 275, 645-650.