era.ee00.md

eraEe00

rv = ERFA.ee00(date1, date2, epsa, dpsi)

The equation of the equinoxes, compatible with IAU 2000 resolutions, given the nutation in longitude and the mean obliquity.

Given:

   date1,date2  double    TT as a 2-part Julian Date (Note 1)
   epsa         double    mean obliquity (Note 2)
   dpsi         double    nutation in longitude (Note 3)

Returned (function value):

                double    equation of the equinoxes (Note 4)

Notes:

1. The TT date date1+date2 is a Julian Date, apportioned in any convenient way between the two arguments. For example, JD(TT)=2450123.7 could be expressed in any of these ways, among others:

          date1          date2

       2450123.7           0.0       (JD method)
       2451545.0       -1421.3       (J2000 method)
       2400000.5       50123.2       (MJD method)
       2450123.5           0.2       (date & time method)

The JD method is the most natural and convenient to use in cases where the loss of several decimal digits of resolution is acceptable. The J2000 method is best matched to the way the argument is handled internally and will deliver the optimum resolution. The MJD method and the date & time methods are both good compromises between resolution and convenience.

2. The obliquity, in radians, is mean of date.

3. The result, which is in radians, operates in the following sense:

      Greenwich apparent ST = GMST + equation of the equinoxes

4. The result is compatible with the IAU 2000 resolutions. For further details, see IERS Conventions 2003 and Capitaine et al. (2002).

Called:

   eraEect00    equation of the equinoxes complementary terms

References:

Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to implement the IAU 2000 definition of UT1", Astronomy & Astrophysics, 406, 1135-1149 (2003)

McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003), IERS Technical Note No. 32, BKG (2004)

This revision: 2021 May 11

Copyright (C) 2013-2021, NumFOCUS Foundation. Derived, with permission, from the SOFA library.