source: branches/FACT++_part_filenames/erfa/src/ldsun.c@ 18795

Last change on this file since 18795 was 18711, checked in by tbretz, 8 years ago
Updated to ERFA 1.3.0 (no relevant code change except the leap second at the beginning of 2017)
File size: 4.4 KB
Line 
1#include "erfa.h"
2
3void eraLdsun(double p[3], double e[3], double em, double p1[3])
4/*
5** - - - - - - - - -
6** e r a L d s u n
7** - - - - - - - - -
8**
9** Deflection of starlight by the Sun.
10**
11** Given:
12** p double[3] direction from observer to star (unit vector)
13** e double[3] direction from Sun to observer (unit vector)
14** em double distance from Sun to observer (au)
15**
16** Returned:
17** p1 double[3] observer to deflected star (unit vector)
18**
19** Notes:
20**
21** 1) The source is presumed to be sufficiently distant that its
22** directions seen from the Sun and the observer are essentially
23** the same.
24**
25** 2) The deflection is restrained when the angle between the star and
26** the center of the Sun is less than a threshold value, falling to
27** zero deflection for zero separation. The chosen threshold value
28** is within the solar limb for all solar-system applications, and
29** is about 5 arcminutes for the case of a terrestrial observer.
30**
31** 3) The arguments p and p1 can be the same array.
32**
33** Called:
34** eraLd light deflection by a solar-system body
35**
36** Copyright (C) 2013-2016, NumFOCUS Foundation.
37** Derived, with permission, from the SOFA library. See notes at end of file.
38*/
39{
40 double em2, dlim;
41
42
43/* Deflection limiter (smaller for distant observers). */
44 em2 = em*em;
45 if ( em2 < 1.0 ) em2 = 1.0;
46 dlim = 1e-6 / (em2 > 1.0 ? em2 : 1.0);
47
48/* Apply the deflection. */
49 eraLd(1.0, p, p, e, em, dlim, p1);
50
51/* Finished. */
52
53}
54/*----------------------------------------------------------------------
55**
56**
57** Copyright (C) 2013-2016, NumFOCUS Foundation.
58** All rights reserved.
59**
60** This library is derived, with permission, from the International
61** Astronomical Union's "Standards of Fundamental Astronomy" library,
62** available from http://www.iausofa.org.
63**
64** The ERFA version is intended to retain identical functionality to
65** the SOFA library, but made distinct through different function and
66** file names, as set out in the SOFA license conditions. The SOFA
67** original has a role as a reference standard for the IAU and IERS,
68** and consequently redistribution is permitted only in its unaltered
69** state. The ERFA version is not subject to this restriction and
70** therefore can be included in distributions which do not support the
71** concept of "read only" software.
72**
73** Although the intent is to replicate the SOFA API (other than
74** replacement of prefix names) and results (with the exception of
75** bugs; any that are discovered will be fixed), SOFA is not
76** responsible for any errors found in this version of the library.
77**
78** If you wish to acknowledge the SOFA heritage, please acknowledge
79** that you are using a library derived from SOFA, rather than SOFA
80** itself.
81**
82**
83** TERMS AND CONDITIONS
84**
85** Redistribution and use in source and binary forms, with or without
86** modification, are permitted provided that the following conditions
87** are met:
88**
89** 1 Redistributions of source code must retain the above copyright
90** notice, this list of conditions and the following disclaimer.
91**
92** 2 Redistributions in binary form must reproduce the above copyright
93** notice, this list of conditions and the following disclaimer in
94** the documentation and/or other materials provided with the
95** distribution.
96**
97** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
98** the International Astronomical Union nor the names of its
99** contributors may be used to endorse or promote products derived
100** from this software without specific prior written permission.
101**
102** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
103** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
104** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
105** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
106** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
107** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
108** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
109** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
110** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
111** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
112** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
113** POSSIBILITY OF SUCH DAMAGE.
114**
115*/
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