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obliq.c@ 1719

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Last change on this file since 1719 was 1719, checked in by cmv, 24 years ago
Adapted to version 3.5 xephem cmv 22/10/2001
File size: 774 bytes

Rev	Line
[1457]	1	#include <stdio.h>
	2
	3	#include "P_.h"
	4	#include "astro.h"
	5
	6	/* given the modified Julian date, mjd, find the mean obliquity of the
	7	* ecliptic, *eps, in radians.
	8	*
	9	* IAU expression (see e.g. Astron. Almanac 1984); stern
	10	*/
	11	void
	12	obliquity (mjd, eps)
	13	double mjd;
	14	double *eps;
	15	{
	16	static double lastmjd = -16347, lasteps;
	17
	18	if (mjd != lastmjd) {
	19	double t = (mjd - J2000)/36525.; /* centuries from J2000 */
	20	lasteps = degrad(23.4392911 + /* 23^ 26' 21".448 */
	21	t * (-46.8150 +
	22	t * ( -0.00059 +
	23	t * ( 0.001813 )))/3600.0);
	24	lastmjd = mjd;
	25	}
	26	*eps = lasteps;
	27	}
	28
	29	/* For RCS Only -- Do Not Edit */
[1719]	30	static char rcsid[2] = {(char )rcsid, "@(#) $RCSfile: obliq.c,v $ $Date: 2001-10-22 12:08:27 $ $Revision: 1.2 $ $Name: not supported by cvs2svn $"};

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