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#include "erfa.h" |
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void eraLteqec(double epj, double dr, double dd, double *dl, double *db) |
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/* |
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** - - - - - - - - - - |
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** e r a L t e q e c |
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** - - - - - - - - - - |
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** |
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** Transformation from ICRS equatorial coordinates to ecliptic |
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** coordinates (mean equinox and ecliptic of date) using a long-term |
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** precession model. |
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** |
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** Given: |
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** epj double Julian epoch (TT) |
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** dr,dd double ICRS right ascension and declination (radians) |
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** |
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** Returned: |
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** dl,db double ecliptic longitude and latitude (radians) |
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** |
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** 1) No assumptions are made about whether the coordinates represent |
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** starlight and embody astrometric effects such as parallax or |
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** aberration. |
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** |
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** 2) The transformation is approximately that from mean J2000.0 right |
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** ascension and declination to ecliptic longitude and latitude |
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** (mean equinox and ecliptic of date), with only frame bias (always |
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** less than 25 mas) to disturb this classical picture. |
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** |
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** 3) The Vondrak et al. (2011, 2012) 400 millennia precession model |
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** agrees with the IAU 2006 precession at J2000.0 and stays within |
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** 100 microarcseconds during the 20th and 21st centuries. It is |
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** accurate to a few arcseconds throughout the historical period, |
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** worsening to a few tenths of a degree at the end of the |
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** +/- 200,000 year time span. |
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** |
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** Called: |
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** eraS2c spherical coordinates to unit vector |
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** eraLtecm J2000.0 to ecliptic rotation matrix, long term |
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** eraRxp product of r-matrix and p-vector |
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** eraC2s unit vector to spherical coordinates |
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** eraAnp normalize angle into range 0 to 2pi |
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** eraAnpm normalize angle into range +/- pi |
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** |
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** References: |
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** |
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** Vondrak, J., Capitaine, N. and Wallace, P., 2011, New precession |
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** expressions, valid for long time intervals, Astron.Astrophys. 534, |
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** A22 |
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** |
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** Vondrak, J., Capitaine, N. and Wallace, P., 2012, New precession |
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** expressions, valid for long time intervals (Corrigendum), |
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** Astron.Astrophys. 541, C1 |
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** |
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** Copyright (C) 2013-2020, 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 rm[3][3], v1[3], v2[3], a, b; |
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/* Spherical to Cartesian. */ |
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eraS2c(dr, dd, v1); |
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/* Rotation matrix, ICRS equatorial to ecliptic. */ |
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eraLtecm(epj, rm); |
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/* The transformation from ICRS to ecliptic. */ |
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eraRxp(rm, v1, v2); |
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/* Cartesian to spherical. */ |
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eraC2s(v2, &a, &b); |
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/* Express in conventional ranges. */ |
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*dl = eraAnp(a); |
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*db = eraAnpm(b); |
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} |
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/*---------------------------------------------------------------------- |
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** |
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** |
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** Copyright (C) 2013-2020, 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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*/ |