eqeq94¶

erfa.eqeq94(date1, date2)[source]¶

Equation of the equinoxes, IAU 1994 model.

Parameters:

date1double array
date2double array

Returns:

c_retvaldouble array

Notes

Wraps ERFA function eraEqeq94. The ERFA documentation is:

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 e r a E q e q 9 4
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Equation of the equinoxes, IAU 1994 model.

Given:
   date1,date2   double     TDB date (Note 1)

Returned (function value):
                 double     equation of the equinoxes (Note 2)

Notes:

1) The 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 result, which is in radians, operates in the following sense:

      Greenwich apparent ST = GMST + equation of the equinoxes

Called:
   eraAnpm      normalize angle into range +/- pi
   eraNut80     nutation, IAU 1980
   eraObl80     mean obliquity, IAU 1980

References:

   IAU Resolution C7, Recommendation 3 (1994).

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

This revision:  2021 May 11

Copyright (C) 2013-2023, NumFOCUS Foundation.
Derived, with permission, from the SOFA library.  See notes at end of file.

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eqeq94¶