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#include "erfa.h" |
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double eraEe00b(double date1, double date2) |
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/* |
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** - - - - - - - - - |
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** e r a E e 0 0 b |
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** - - - - - - - - - |
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** |
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** Equation of the equinoxes, compatible with IAU 2000 resolutions but |
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** using the truncated nutation model IAU 2000B. |
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** |
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** Given: |
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** date1,date2 double TT as a 2-part Julian Date (Note 1) |
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** |
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** Returned (function value): |
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** double equation of the equinoxes (Note 2) |
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** |
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** Notes: |
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** |
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** 1) The TT date date1+date2 is a Julian Date, apportioned in any |
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** convenient way between the two arguments. For example, |
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** JD(TT)=2450123.7 could be expressed in any of these ways, |
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** among others: |
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** |
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** date1 date2 |
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** |
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** 2450123.7 0.0 (JD method) |
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** 2451545.0 -1421.3 (J2000 method) |
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** 2400000.5 50123.2 (MJD method) |
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** 2450123.5 0.2 (date & time method) |
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** |
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** The JD method is the most natural and convenient to use in |
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** cases where the loss of several decimal digits of resolution |
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** is acceptable. The J2000 method is best matched to the way |
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** the argument is handled internally and will deliver the |
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** optimum resolution. The MJD method and the date & time methods |
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** are both good compromises between resolution and convenience. |
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** |
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** 2) The result, which is in radians, operates in the following sense: |
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** |
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** Greenwich apparent ST = GMST + equation of the equinoxes |
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** |
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** 3) The result is compatible with the IAU 2000 resolutions except |
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** that accuracy has been compromised for the sake of speed. For |
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** further details, see McCarthy & Luzum (2001), IERS Conventions |
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** 2003 and Capitaine et al. (2003). |
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** |
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** Called: |
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** eraPr00 IAU 2000 precession adjustments |
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** eraObl80 mean obliquity, IAU 1980 |
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** eraNut00b nutation, IAU 2000B |
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** eraEe00 equation of the equinoxes, IAU 2000 |
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** |
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** References: |
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** |
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** Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to |
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** implement the IAU 2000 definition of UT1", Astronomy & |
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** Astrophysics, 406, 1135-1149 (2003) |
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** |
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** McCarthy, D.D. & Luzum, B.J., "An abridged model of the |
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** precession-nutation of the celestial pole", Celestial Mechanics & |
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** Dynamical Astronomy, 85, 37-49 (2003) |
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** |
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** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003), |
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** IERS Technical Note No. 32, BKG (2004) |
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** |
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** Copyright (C) 2013-2019, NumFOCUS Foundation. |
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** Derived, with permission, from the SOFA library. See notes at end of file. |
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*/ |
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{ |
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double dpsipr, depspr, epsa, dpsi, deps, ee; |
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/* IAU 2000 precession-rate adjustments. */ |
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eraPr00(date1, date2, &dpsipr, &depspr); |
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/* Mean obliquity, consistent with IAU 2000 precession-nutation. */ |
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epsa = eraObl80(date1, date2) + depspr; |
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/* Nutation in longitude. */ |
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eraNut00b(date1, date2, &dpsi, &deps); |
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/* Equation of the equinoxes. */ |
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ee = eraEe00(date1, date2, epsa, dpsi); |
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return ee; |
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} |
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/*---------------------------------------------------------------------- |
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** |
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** |
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** Copyright (C) 2013-2019, NumFOCUS Foundation. |
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** All rights reserved. |
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** |
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** This library is derived, with permission, from the International |
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** Astronomical Union's "Standards of Fundamental Astronomy" library, |
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** available from http://www.iausofa.org. |
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** |
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** The ERFA version is intended to retain identical functionality to |
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** the SOFA library, but made distinct through different function and |
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** file names, as set out in the SOFA license conditions. The SOFA |
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** original has a role as a reference standard for the IAU and IERS, |
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** and consequently redistribution is permitted only in its unaltered |
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** state. The ERFA version is not subject to this restriction and |
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** therefore can be included in distributions which do not support the |
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** concept of "read only" software. |
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** |
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** Although the intent is to replicate the SOFA API (other than |
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** replacement of prefix names) and results (with the exception of |
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** bugs; any that are discovered will be fixed), SOFA is not |
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** responsible for any errors found in this version of the library. |
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** |
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** If you wish to acknowledge the SOFA heritage, please acknowledge |
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** that you are using a library derived from SOFA, rather than SOFA |
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** itself. |
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** |
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** |
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** TERMS AND CONDITIONS |
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** |
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** Redistribution and use in source and binary forms, with or without |
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** modification, are permitted provided that the following conditions |
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** are met: |
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** |
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** 1 Redistributions of source code must retain the above copyright |
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** notice, this list of conditions and the following disclaimer. |
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** |
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** 2 Redistributions in binary form must reproduce the above copyright |
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** notice, this list of conditions and the following disclaimer in |
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** the documentation and/or other materials provided with the |
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** distribution. |
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** |
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** 3 Neither the name of the Standards Of Fundamental Astronomy Board, |
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** the International Astronomical Union nor the names of its |
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** contributors may be used to endorse or promote products derived |
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** from this software without specific prior written permission. |
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** |
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** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
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** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
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** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
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** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
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** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
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** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER |
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** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |
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** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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** POSSIBILITY OF SUCH DAMAGE. |
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** |
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*/ |