ee00b.c

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#include "erfa.h"

double eraEe00b(double date1, double date2)
/*
**  - - - - - - - - -
**   e r a E e 0 0 b
**  - - - - - - - - -
**
**  Equation of the equinoxes, compatible with IAU 2000 resolutions but
**  using the truncated nutation model IAU 2000B.
**
**  Given:
**     date1,date2  double    TT as a 2-part Julian Date (Note 1)
**
**  Returned (function value):
**                  double    equation of the equinoxes (Note 2)
**
**  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 result, which is in radians, operates in the following sense:
**
**        Greenwich apparent ST = GMST + equation of the equinoxes
**
**  3) The result is compatible with the IAU 2000 resolutions except
**     that accuracy has been compromised for the sake of speed.  For
**     further details, see McCarthy & Luzum (2001), IERS Conventions
**     2003 and Capitaine et al. (2003).
**
**  Called:
**     eraPr00      IAU 2000 precession adjustments
**     eraObl80     mean obliquity, IAU 1980
**     eraNut00b    nutation, IAU 2000B
**     eraEe00      equation of the equinoxes, IAU 2000
**
**  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. & Luzum, B.J., "An abridged model of the
**     precession-nutation of the celestial pole", Celestial Mechanics &
**     Dynamical Astronomy, 85, 37-49 (2003)
**
**     McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
**     IERS Technical Note No. 32, BKG (2004)
**
**  Copyright (C) 2013-2015, NumFOCUS Foundation.
**  Derived, with permission, from the SOFA library.  See notes at end of file.
*/
{
   double dpsipr, depspr, epsa, dpsi, deps, ee;

/* IAU 2000 precession-rate adjustments. */
   eraPr00(date1, date2, &dpsipr, &depspr);

/* Mean obliquity, consistent with IAU 2000 precession-nutation. */
   epsa = eraObl80(date1, date2) + depspr;

/* Nutation in longitude. */
   eraNut00b(date1, date2, &dpsi, &deps);

/* Equation of the equinoxes. */
   ee = eraEe00(date1, date2, epsa, dpsi);

   return ee;

}
/*----------------------------------------------------------------------
**  
**  
**  Copyright (C) 2013-2015, NumFOCUS Foundation.
**  All rights reserved.
**  
**  This library is derived, with permission, from the International
**  Astronomical Union's "Standards of Fundamental Astronomy" library,
**  available from http://www.iausofa.org.
**  
**  The ERFA version is intended to retain identical functionality to
**  the SOFA library, but made distinct through different function and
**  file names, as set out in the SOFA license conditions.  The SOFA
**  original has a role as a reference standard for the IAU and IERS,
**  and consequently redistribution is permitted only in its unaltered
**  state.  The ERFA version is not subject to this restriction and
**  therefore can be included in distributions which do not support the
**  concept of "read only" software.
**  
**  Although the intent is to replicate the SOFA API (other than
**  replacement of prefix names) and results (with the exception of
**  bugs;  any that are discovered will be fixed), SOFA is not
**  responsible for any errors found in this version of the library.
**  
**  If you wish to acknowledge the SOFA heritage, please acknowledge
**  that you are using a library derived from SOFA, rather than SOFA
**  itself.
**  
**  
**  TERMS AND CONDITIONS
**  
**  Redistribution and use in source and binary forms, with or without
**  modification, are permitted provided that the following conditions
**  are met:
**  
**  1 Redistributions of source code must retain the above copyright
**    notice, this list of conditions and the following disclaimer.
**  
**  2 Redistributions in binary form must reproduce the above copyright
**    notice, this list of conditions and the following disclaimer in
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**    distribution.
**  
**  3 Neither the name of the Standards Of Fundamental Astronomy Board,
**    the International Astronomical Union nor the names of its
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**    from this software without specific prior written permission.
**  
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*/