#include "erfa.h" void eraFk5hz(double r5, double d5, double date1, double date2, double *rh, double *dh) /* ** - - - - - - - - - ** e r a F k 5 h z ** - - - - - - - - - ** ** Transform an FK5 (J2000.0) star position into the system of the ** Hipparcos catalogue, assuming zero Hipparcos proper motion. ** ** Given: ** r5 double FK5 RA (radians), equinox J2000.0, at date ** d5 double FK5 Dec (radians), equinox J2000.0, at date ** date1,date2 double TDB date (Notes 1,2) ** ** Returned: ** rh double Hipparcos RA (radians) ** dh double Hipparcos Dec (radians) ** ** Notes: ** ** 1) This function converts a star position from the FK5 system to ** the Hipparcos system, in such a way that the Hipparcos proper ** motion is zero. Because such a star has, in general, a non-zero ** proper motion in the FK5 system, the function requires the date ** at which the position in the FK5 system was determined. ** ** 2) 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. ** ** 3) The FK5 to Hipparcos transformation is modeled as a pure ** rotation and spin; zonal errors in the FK5 catalogue are not ** taken into account. ** ** 4) The position returned by this function is in the Hipparcos ** reference system but at date date1+date2. ** ** 5) See also eraFk52h, eraH2fk5, eraHfk5z. ** ** Called: ** eraS2c spherical coordinates to unit vector ** eraFk5hip FK5 to Hipparcos rotation and spin ** eraSxp multiply p-vector by scalar ** eraRv2m r-vector to r-matrix ** eraTrxp product of transpose of r-matrix and p-vector ** eraPxp vector product of two p-vectors ** eraC2s p-vector to spherical ** eraAnp normalize angle into range 0 to 2pi ** ** Reference: ** ** F.Mignard & M.Froeschle, 2000, Astron.Astrophys. 354, 732-739. ** ** Copyright (C) 2013-2017, NumFOCUS Foundation. ** Derived, with permission, from the SOFA library. See notes at end of file. */ { double t, p5e[3], r5h[3][3], s5h[3], vst[3], rst[3][3], p5[3], ph[3], w; /* Interval from given date to fundamental epoch J2000.0 (JY). */ t = - ((date1 - ERFA_DJ00) + date2) / ERFA_DJY; /* FK5 barycentric position vector. */ eraS2c(r5, d5, p5e); /* FK5 to Hipparcos orientation matrix and spin vector. */ eraFk5hip(r5h, s5h); /* Accumulated Hipparcos wrt FK5 spin over that interval. */ eraSxp(t, s5h, vst); /* Express the accumulated spin as a rotation matrix. */ eraRv2m(vst, rst); /* Derotate the vector's FK5 axes back to date. */ eraTrxp(rst, p5e, p5); /* Rotate the vector into the Hipparcos system. */ eraRxp(r5h, p5, ph); /* Hipparcos vector to spherical. */ eraC2s(ph, &w, dh); *rh = eraAnp(w); return; } /*---------------------------------------------------------------------- ** ** ** Copyright (C) 2013-2017, 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 ** the documentation and/or other materials provided with the ** distribution. ** ** 3 Neither the name of the Standards Of Fundamental Astronomy Board, ** the International Astronomical Union nor the names of its ** contributors may be used to endorse or promote products derived ** from this software without specific prior written permission. ** ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; ** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER ** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT ** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE ** POSSIBILITY OF SUCH DAMAGE. ** */