pom.c revision 2490
1/* 2 * Copyright (c) 1989, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software posted to USENET. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36#ifndef lint 37static char copyright[] = 38"@(#) Copyright (c) 1989, 1993\n\ 39 The Regents of the University of California. All rights reserved.\n"; 40#endif /* not lint */ 41 42#ifndef lint 43static char sccsid[] = "@(#)pom.c 8.1 (Berkeley) 5/31/93"; 44#endif /* not lint */ 45 46/* 47 * Phase of the Moon. Calculates the current phase of the moon. 48 * Based on routines from `Practical Astronomy with Your Calculator', 49 * by Duffett-Smith. Comments give the section from the book that 50 * particular piece of code was adapted from. 51 * 52 * -- Keith E. Brandt VIII 1984 53 * 54 */ 55 56#include <sys/time.h> 57#include <stdio.h> 58#include <tzfile.h> 59#include <math.h> 60 61#define PI 3.141592654 62#define EPOCH 85 63#define EPSILONg 279.611371 /* solar ecliptic long at EPOCH */ 64#define RHOg 282.680403 /* solar ecliptic long of perigee at EPOCH */ 65#define ECCEN 0.01671542 /* solar orbit eccentricity */ 66#define lzero 18.251907 /* lunar mean long at EPOCH */ 67#define Pzero 192.917585 /* lunar mean long of perigee at EPOCH */ 68#define Nzero 55.204723 /* lunar mean long of node at EPOCH */ 69 70double dtor(), potm(), adj360(); 71 72main() 73{ 74 extern int errno; 75 struct timeval tp; 76 struct timezone tzp; 77 struct tm *GMT, *gmtime(); 78 double days, today, tomorrow; 79 int cnt; 80 char *strerror(); 81 82 if (gettimeofday(&tp,&tzp)) { 83 (void)fprintf(stderr, "pom: %s\n", strerror(errno)); 84 exit(1); 85 } 86 GMT = gmtime(&tp.tv_sec); 87 days = (GMT->tm_yday + 1) + ((GMT->tm_hour + 88 (GMT->tm_min / 60.0) + (GMT->tm_sec / 3600.0)) / 24.0); 89 for (cnt = EPOCH; cnt < GMT->tm_year; ++cnt) 90 days += isleap(cnt) ? 366 : 365; 91 today = potm(days) + .5; 92 (void)printf("The Moon is "); 93 if ((int)today == 100) 94 (void)printf("Full\n"); 95 else if (!(int)today) 96 (void)printf("New\n"); 97 else { 98 tomorrow = potm(days + 1); 99 if ((int)today == 50) 100 (void)printf("%s\n", tomorrow > today ? 101 "at the First Quarter" : "at the Last Quarter"); 102 else { 103 (void)printf("%s ", tomorrow > today ? 104 "Waxing" : "Waning"); 105 if (today > 50) 106 (void)printf("Gibbous (%1.0f%% of Full)\n", 107 today); 108 else if (today < 50) 109 (void)printf("Crescent (%1.0f%% of Full)\n", 110 today); 111 } 112 } 113} 114 115/* 116 * potm -- 117 * return phase of the moon 118 */ 119double 120potm(days) 121 double days; 122{ 123 double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime; 124 double A4, lprime, V, ldprime, D, Nm; 125 126 N = 360 * days / 365.2422; /* sec 42 #3 */ 127 adj360(&N); 128 Msol = N + EPSILONg - RHOg; /* sec 42 #4 */ 129 adj360(&Msol); 130 Ec = 360 / PI * ECCEN * sin(dtor(Msol)); /* sec 42 #5 */ 131 LambdaSol = N + Ec + EPSILONg; /* sec 42 #6 */ 132 adj360(&LambdaSol); 133 l = 13.1763966 * days + lzero; /* sec 61 #4 */ 134 adj360(&l); 135 Mm = l - (0.1114041 * days) - Pzero; /* sec 61 #5 */ 136 adj360(&Mm); 137 Nm = Nzero - (0.0529539 * days); /* sec 61 #6 */ 138 adj360(&Nm); 139 Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm)); /* sec 61 #7 */ 140 Ac = 0.1858 * sin(dtor(Msol)); /* sec 61 #8 */ 141 A3 = 0.37 * sin(dtor(Msol)); 142 Mmprime = Mm + Ev - Ac - A3; /* sec 61 #9 */ 143 Ec = 6.2886 * sin(dtor(Mmprime)); /* sec 61 #10 */ 144 A4 = 0.214 * sin(dtor(2 * Mmprime)); /* sec 61 #11 */ 145 lprime = l + Ev + Ec - Ac + A4; /* sec 61 #12 */ 146 V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol))); /* sec 61 #13 */ 147 ldprime = lprime + V; /* sec 61 #14 */ 148 D = ldprime - LambdaSol; /* sec 63 #2 */ 149 return(50 * (1 - cos(dtor(D)))); /* sec 63 #3 */ 150} 151 152/* 153 * dtor -- 154 * convert degrees to radians 155 */ 156double 157dtor(deg) 158 double deg; 159{ 160 return(deg * PI / 180); 161} 162 163/* 164 * adj360 -- 165 * adjust value so 0 <= deg <= 360 166 */ 167double 168adj360(deg) 169 double *deg; 170{ 171 for (;;) 172 if (*deg < 0) 173 *deg += 360; 174 else if (*deg > 360) 175 *deg -= 360; 176 else 177 break; 178} 179