DOUBLE PRECISION FUNCTION iau_EQEQ94 ( DATE1, DATE2 ) *+ * - - - - - - - - - - - * i a u _ E Q E Q 9 4 * - - - - - - - - - - - * * Equation of the equinoxes, IAU 1994 model. * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: canonical model. * * Given: * DATE1,DATE2 d TDB date (Note 1) * * Returned: * iau_EQEQ94 d equation of the equinoxes (Note 2) * * Notes: * * 1) The date DATE1+DATE2 is a Julian Date, apportioned in any * convenient way between the two arguments. For example, * JD(TDB)=2450123.7 could be expressed in any of these ways, * among others: * * DATE1 DATE2 * * 2450123.7D0 0D0 (JD method) * 2451545D0 -1421.3D0 (J2000 method) * 2400000.5D0 50123.2D0 (MJD method) * 2450123.5D0 0.2D0 (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. * * 2) The result, which is in radians, operates in the following sense: * * Greenwich apparent ST = GMST + equation of the equinoxes * * Called: * iau_NUT80 nutation, IAU 1980 * iau_OBL80 mean obliquity, IAU 1980 * iau_ANPM normalize angle into range +/- pi * * References: * * IAU Resolution C7, Recommendation 3 (1994) * * Capitaine, N. & Gontier, A.-M., Astron. Astrophys., 275, * 645-650 (1993) * * This revision: 2008 May 24 * * Copyright (C) 2008 IAU SOFA Review Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION DATE1, DATE2 * Arcseconds to radians DOUBLE PRECISION DAS2R PARAMETER ( DAS2R = 4.848136811095359935899141D-6 ) * 2Pi DOUBLE PRECISION D2PI PARAMETER (D2PI = 6.283185307179586476925287D0) * Reference epoch (J2000), JD DOUBLE PRECISION DJ00 PARAMETER ( DJ00 = 2451545D0 ) * Days per Julian century DOUBLE PRECISION DJC PARAMETER ( DJC = 36525D0 ) DOUBLE PRECISION T, OM, DPSI, DEPS, EPS0 DOUBLE PRECISION iau_ANPM, iau_OBL80 * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Interval between fundamental epoch J2000.0 and given date (JC). T = ( ( DATE1-DJ00 ) + DATE2 ) / DJC * Longitude of the mean ascending node of the lunar orbit on the * ecliptic, measured from the mean equinox of date. OM = iau_ANPM( ( 450160.280D0 + ( -482890.539D0 + : ( 7.455D0 + 0.008D0 * T ) * T ) * T ) * DAS2R : + MOD(-5D0*T,1D0) * D2PI ) * Nutation components and mean obliquity. CALL iau_NUT80 ( DATE1, DATE2, DPSI, DEPS ) EPS0 = iau_OBL80 ( DATE1, DATE2 ) * Equation of the equinoxes. iau_EQEQ94 = DPSI * COS(EPS0) + DAS2R * ( 0.00264D0 * SIN(OM) + : 0.000063D0 * SIN(OM+OM)) * Finished. *+----------------------------------------------------------------------- * * Copyright (C) 2008 * Standards Of Fundamental Astronomy Review Board * of the International Astronomical Union. * * ===================== * SOFA Software License * ===================== * * NOTICE TO USER: * * BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING TERMS AND CONDITIONS * WHICH APPLY TO ITS USE. * * 1. The Software is owned by the IAU SOFA Review Board ("the Board"). * * 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 adapt the SOFA software and its * algorithms for your own purposes and you may copy and distribute * a resulting "derived work" to others on a world-wide, royalty-free * basis, provided that the derived work complies 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 contain * software provided by SOFA or software that has been distributed * by or endorsed by SOFA. * * b) The source code of your derived work must contain descriptions * of how the derived work is based upon and/or differs from the * original SOFA software. * * c) The name(s) of all routine(s) that you distribute shall differ * from the SOFA names, even when the SOFA content has not been * otherwise changed. * * d) The routine-naming prefix "iau" shall not be used. * * e) 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. * * f) 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. * * 4. In any published work or commercial products which includes * results achieved by using the SOFA software, you shall acknowledge * that the SOFA software was used in obtaining those results. * * 5. You shall not cause the SOFA software to be brought into * disrepute, either by misuse, or use for inappropriate tasks, or by * inappropriate modification. * * 6. The SOFA software is provided "as is" and the Board makes no * warranty as to its use or performance. The Board does not and * cannot warrant the performance or results which the user may obtain * by using the SOFA software. The Board 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 the Board be liable to the user for any consequential, * incidental, or special damages, including any lost profits or lost * savings, even if a Board representative has been advised of such * damages, or for any claim by any third party. * * 7. 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. * * Correspondence concerning SOFA software should be addressed as * follows: * * Internet email: sofa@rl.ac.uk * Postal address: IAU SOFA Center * Rutherford Appleton Laboratory * Chilton, Didcot, Oxon OX11 0QX * United Kingdom * *----------------------------------------------------------------------- END