FACT++  1.0
ee06a.c
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1 #include "erfa.h"
2 
3 double eraEe06a(double date1, double date2)
4 /*
5 ** - - - - - - - - -
6 ** e r a E e 0 6 a
7 ** - - - - - - - - -
8 **
9 ** Equation of the equinoxes, compatible with IAU 2000 resolutions and
10 ** IAU 2006/2000A precession-nutation.
11 **
12 ** Given:
13 ** date1,date2 double TT as a 2-part Julian Date (Note 1)
14 **
15 ** Returned (function value):
16 ** double equation of the equinoxes (Note 2)
17 **
18 ** Notes:
19 **
20 ** 1) The TT date date1+date2 is a Julian Date, apportioned in any
21 ** convenient way between the two arguments. For example,
22 ** JD(TT)=2450123.7 could be expressed in any of these ways,
23 ** among others:
24 **
25 ** date1 date2
26 **
27 ** 2450123.7 0.0 (JD method)
28 ** 2451545.0 -1421.3 (J2000 method)
29 ** 2400000.5 50123.2 (MJD method)
30 ** 2450123.5 0.2 (date & time method)
31 **
32 ** The JD method is the most natural and convenient to use in
33 ** cases where the loss of several decimal digits of resolution
34 ** is acceptable. The J2000 method is best matched to the way
35 ** the argument is handled internally and will deliver the
36 ** optimum resolution. The MJD method and the date & time methods
37 ** are both good compromises between resolution and convenience.
38 **
39 ** 2) The result, which is in radians, operates in the following sense:
40 **
41 ** Greenwich apparent ST = GMST + equation of the equinoxes
42 **
43 ** Called:
44 ** eraAnpm normalize angle into range +/- pi
45 ** eraGst06a Greenwich apparent sidereal time, IAU 2006/2000A
46 ** eraGmst06 Greenwich mean sidereal time, IAU 2006
47 **
48 ** Reference:
49 **
50 ** McCarthy, D. D., Petit, G. (eds.), 2004, IERS Conventions (2003),
51 ** IERS Technical Note No. 32, BKG
52 **
53 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
54 ** Derived, with permission, from the SOFA library. See notes at end of file.
55 */
56 {
57  double gst06a, gmst06, ee;
58 
59 /* Apparent and mean sidereal times. */
60  gst06a = eraGst06a(0.0, 0.0, date1, date2);
61  gmst06 = eraGmst06(0.0, 0.0, date1, date2);
62 
63 /* Equation of the equinoxes. */
64  ee = eraAnpm(gst06a - gmst06);
65 
66  return ee;
67 
68 }
69 /*----------------------------------------------------------------------
70 **
71 **
72 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
73 ** All rights reserved.
74 **
75 ** This library is derived, with permission, from the International
76 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
77 ** available from http://www.iausofa.org.
78 **
79 ** The ERFA version is intended to retain identical functionality to
80 ** the SOFA library, but made distinct through different function and
81 ** file names, as set out in the SOFA license conditions. The SOFA
82 ** original has a role as a reference standard for the IAU and IERS,
83 ** and consequently redistribution is permitted only in its unaltered
84 ** state. The ERFA version is not subject to this restriction and
85 ** therefore can be included in distributions which do not support the
86 ** concept of "read only" software.
87 **
88 ** Although the intent is to replicate the SOFA API (other than
89 ** replacement of prefix names) and results (with the exception of
90 ** bugs; any that are discovered will be fixed), SOFA is not
91 ** responsible for any errors found in this version of the library.
92 **
93 ** If you wish to acknowledge the SOFA heritage, please acknowledge
94 ** that you are using a library derived from SOFA, rather than SOFA
95 ** itself.
96 **
97 **
98 ** TERMS AND CONDITIONS
99 **
100 ** Redistribution and use in source and binary forms, with or without
101 ** modification, are permitted provided that the following conditions
102 ** are met:
103 **
104 ** 1 Redistributions of source code must retain the above copyright
105 ** notice, this list of conditions and the following disclaimer.
106 **
107 ** 2 Redistributions in binary form must reproduce the above copyright
108 ** notice, this list of conditions and the following disclaimer in
109 ** the documentation and/or other materials provided with the
110 ** distribution.
111 **
112 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
113 ** the International Astronomical Union nor the names of its
114 ** contributors may be used to endorse or promote products derived
115 ** from this software without specific prior written permission.
116 **
117 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
118 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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120 ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
121 ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
122 ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
123 ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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128 ** POSSIBILITY OF SUCH DAMAGE.
129 **
130 */
eraGst06a
double eraGst06a(double uta, double utb, double tta, double ttb)
Definition: gst06a.c:3
eraEe06a
double eraEe06a(double date1, double date2)
Definition: ee06a.c:3
eraAnpm
double eraAnpm(double a)
Definition: anpm.c:3
eraGmst06
double eraGmst06(double uta, double utb, double tta, double ttb)
Definition: gmst06.c:3