#include "sofa.h" void iauTpsts(double xi, double eta, double a0, double b0, double *a, double *b) /* ** - - - - - - - - - ** i a u T p s t s ** - - - - - - - - - ** ** In the tangent plane projection, given the star's rectangular ** coordinates and the spherical coordinates of the tangent point, ** solve for the spherical coordinates of the star. ** ** This function is part of the International Astronomical Union's ** SOFA (Standards of Fundamental Astronomy) software collection. ** ** Status: support function. ** ** Given: ** xi,eta double rectangular coordinates of star image (Note 2) ** a0,b0 double tangent point's spherical coordinates ** ** Returned: ** *a,*b double star's spherical coordinates ** ** 1) The tangent plane projection is also called the "gnomonic ** projection" and the "central projection". ** ** 2) The eta axis points due north in the adopted coordinate system. ** If the spherical coordinates are observed (RA,Dec), the tangent ** plane coordinates (xi,eta) are conventionally called the ** "standard coordinates". If the spherical coordinates are with ** respect to a right-handed triad, (xi,eta) are also right-handed. ** The units of (xi,eta) are, effectively, radians at the tangent ** point. ** ** 3) All angular arguments are in radians. ** ** 4) This function is a member of the following set: ** ** spherical vector solve for ** ** iauTpxes iauTpxev xi,eta ** > iauTpsts < iauTpstv star ** iauTpors iauTporv origin ** ** Called: ** iauAnp normalize angle into range 0 to 2pi ** ** References: ** ** Calabretta M.R. & Greisen, E.W., 2002, "Representations of ** celestial coordinates in FITS", Astron.Astrophys. 395, 1077 ** ** Green, R.M., "Spherical Astronomy", Cambridge University Press, ** 1987, Chapter 13. ** ** This revision: 2018 January 2 ** ** SOFA release 2020-07-21 ** ** Copyright (C) 2020 IAU SOFA Board. See notes at end. */ { double sb0, cb0, d; sb0 = sin(b0); cb0 = cos(b0); d = cb0 - eta*sb0; *a = iauAnp(atan2(xi,d) + a0); *b = atan2(sb0+eta*cb0, sqrt(xi*xi+d*d)); /* Finished. */ /*---------------------------------------------------------------------- ** ** Copyright (C) 2020 ** Standards Of Fundamental Astronomy Board ** of the International Astronomical Union. ** ** ===================== ** SOFA Software License ** ===================== ** ** NOTICE TO USER: ** ** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND ** CONDITIONS WHICH APPLY TO ITS USE. ** ** 1. The Software is owned by the IAU SOFA Board ("SOFA"). ** ** 2. Permission is granted to anyone to use the SOFA software for any ** purpose, including commercial applications, free of charge and ** without payment of royalties, subject to the conditions and ** restrictions listed below. ** ** 3. You (the user) may copy and distribute SOFA source code to others, ** and use and adapt its code and algorithms in your own software, ** on a world-wide, royalty-free basis. That portion of your ** distribution that does not consist of intact and unchanged copies ** of SOFA source code files is a "derived work" that must comply ** with the following requirements: ** ** a) Your work shall be marked or carry a statement that it ** (i) uses routines and computations derived by you from ** software provided by SOFA under license to you; and ** (ii) does not itself constitute software provided by and/or ** endorsed by SOFA. ** ** b) The source code of your derived work must contain descriptions ** of how the derived work is based upon, contains and/or differs ** from the original SOFA software. ** ** c) The names of all routines in your derived work shall not ** include the prefix "iau" or "sofa" or trivial modifications ** thereof such as changes of case. ** ** d) The origin of the SOFA components of your derived work must ** not be misrepresented; you must not claim that you wrote the ** original software, nor file a patent application for SOFA ** software or algorithms embedded in the SOFA software. ** ** e) These requirements must be reproduced intact in any source ** distribution and shall apply to anyone to whom you have ** granted a further right to modify the source code of your ** derived work. ** ** Note that, as originally distributed, the SOFA software is ** intended to be a definitive implementation of the IAU standards, ** and consequently third-party modifications are discouraged. All ** variations, no matter how minor, must be explicitly marked as ** such, as explained above. ** ** 4. You shall not cause the SOFA software to be brought into ** disrepute, either by misuse, or use for inappropriate tasks, or ** by inappropriate modification. ** ** 5. The SOFA software is provided "as is" and SOFA makes no warranty ** as to its use or performance. SOFA does not and cannot warrant ** the performance or results which the user may obtain by using the ** SOFA software. SOFA makes no warranties, express or implied, as ** to non-infringement of third party rights, merchantability, or ** fitness for any particular purpose. In no event will SOFA be ** liable to the user for any consequential, incidental, or special ** damages, including any lost profits or lost savings, even if a ** SOFA representative has been advised of such damages, or for any ** claim by any third party. ** ** 6. The provision of any version of the SOFA software under the terms ** and conditions specified herein does not imply that future ** versions will also be made available under the same terms and ** conditions. * ** In any published work or commercial product which uses the SOFA ** software directly, acknowledgement (see www.iausofa.org) is ** appreciated. ** ** Correspondence concerning SOFA software should be addressed as ** follows: ** ** By email: sofa@ukho.gov.uk ** By post: IAU SOFA Center ** HM Nautical Almanac Office ** UK Hydrographic Office ** Admiralty Way, Taunton ** Somerset, TA1 2DN ** United Kingdom ** **--------------------------------------------------------------------*/ }