/*  * This file is part of the UCB release of Plan 9. It is subject to the license * terms in the LICENSE file found in the top-level directory of this * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No * part of the UCB release of Plan 9, including this file, may be copied, * modified, propagated, or distributed except according to the terms contained * in the LICENSE file. */ #include "astro.h" voidnutate(void){ /* *	uses radian, radsec *	sets phi, eps, dphi, deps, obliq, gst, tobliq */ 	double msun, mnom, noded, dmoon; /* *	nutation of the equinoxes is a wobble of the pole *	of the earths rotation whose magnitude is about *	9 seconds of arc and whose period is about 18.6 years. * *	it depends upon the pull of the sun and moon on the *	equatorial bulge of the earth. * *	phi and eps are the two angles which specify the *	true pole with respect to the mean pole. * *	all coeffieients are from Exp. Supp. pp.44-45 */ 	mnom = 296.104608 + 13.0649924465*eday + 9.192e-3*capt2		 + 14.38e-6*capt3;	mnom *= radian;	msun = 358.475833 + .9856002669*eday - .150e-3*capt2		 - 3.33e-6*capt3;	msun *= radian;	noded = 11.250889 + 13.2293504490*eday - 3.211e-3*capt2		 - 0.33e-6*capt3;	noded *= radian;	dmoon = 350.737486 + 12.1907491914*eday - 1.436e-3*capt2		 + 1.89e-6*capt3;	dmoon *= radian;	node = 259.183275 - .0529539222*eday + 2.078e-3*capt2		 + 2.22e-6*capt3;	node *= radian; /* *	long period terms */ 	phi = 0.;	eps = 0.;	dphi = 0.;	deps = 0.;  	icosadd(nutfp, nutcp);	phi = -(17.2327+.01737*capt)*sin(node);	phi += sinadd(4, node, noded, dmoon, msun); 	eps = cosadd(4, node, noded, dmoon, msun); /* *	short period terms */  	dphi = sinadd(4, node, noded, mnom, dmoon); 	deps = cosadd(3, node, noded, mnom); 	phi = (phi+dphi)*radsec;	eps = (eps+deps)*radsec;	dphi *= radsec;	deps *= radsec; 	obliq = 23.452294 - .0130125*capt - 1.64e-6*capt2		 + 0.503e-6*capt3;	obliq *= radian;	tobliq = obliq + eps; 	gst = 99.690983 + 360.9856473354*eday + .000387*capt2;	gst -= 180.;	gst = fmod(gst, 360.);	if(gst < 0.)		gst += 360.;	gst *= radian;	gst += phi*cos(obliq);}