DOUBLE PRECISION FUNCTION iau_EQEQ94 ( EPOCH1, EPOCH2 ) *+ * - - - - - - - - - - - * 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: * EPOCH1,EPOCH2 d TDB epoch (Note 1) * * Returned: * iau_EQEQ94 d equation of the equinoxes (Note 2) * * Notes: * * 1) The epoch EPOCH1+EPOCH2 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: * * EPOCH1 EPOCH2 * * 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 * * References: * * IAU Resolution C7, Recommendation 3 (1994) * * Capitaine, N. & Gontier, A.-M., Astron. Astrophys., 275, * 645-650 (1993) * * This revision: 2001 January 4 * * Copyright (C) 2001 IAU SOFA Review Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE DOUBLE PRECISION EPOCH1, EPOCH2 * 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 DJ0 PARAMETER ( DJ0 = 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 epoch (JC). T = ( ( EPOCH1-DJ0 ) + EPOCH2 ) / 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 ( EPOCH1, EPOCH2, DPSI, DEPS ) EPS0 = iau_OBL80 ( EPOCH1, EPOCH2 ) * Equation of the equinoxes. iau_EQEQ94 = DPSI * COS(EPS0) + DAS2R * ( 0.00264D0 * SIN(OM) + : 0.000063D0 * SIN(OM+OM)) * Finished. *+---------------------------------------------------------------------- * * Copyright (C) 2001 * 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. The Software is made available free of charge for use by: * * a) private individuals for non-profit research; and * * b) non-profit educational, academic and research institutions. * * 3. Commercial use of the Software is specifically excluded from the * terms and conditions of this license. Commercial use of the * Software is subject to the prior written agreement of the Board on * terms to be agreed. * * 4. The provision of any version of the 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. * * 5. The user may modify the Software for his/her own purposes. The * user may distribute the modified software provided that the Board * is informed and that a copy of the modified software is made * available to the Board on request. All modifications made by the * user shall be clearly identified to show how the modified software * differs from the original Software, and the name(s) of the * affected routine(s) shall be changed. The original SOFA Software * License text must be present. * * 6. In any published work produced by the user and which includes * results achieved by using the Software, the user shall acknowledge * that the Software was used in producing the information contained * in such publication. * * 7. The user may incorporate or embed the Software into other software * products which he/she may then give away free of charge but not * sell provided the user makes due acknowledgement of the use which * he/she has made of the Software in creating such software * products. Any redistribution of the Software in this way shall be * made under the same terms and conditions under which the user * received it from the SOFA Center. * * 8. The user shall not cause the Software to be brought into * disrepute, either by misuse, or use for inappropriate tasks, or by * inappropriate modification. * * 9. The Software is provided to the user "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 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. * * 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