pom.c revision 1.2
1 /* 2 * Copyright (c) 1989 The Regents of the University of California. 3 * 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 37 char copyright[] = 38 "@(#) Copyright (c) 1989 The Regents of the University of California.\n\ 39 All rights reserved.\n"; 40 #endif /* not lint */ 41 42 #ifndef lint 43 /*static char sccsid[] = "from: @(#)pom.c 5.3 (Berkeley) 2/28/91";*/ 44 static char rcsid[] = "$Id: pom.c,v 1.2 1993/08/01 18:53:16 mycroft Exp $"; 45 #endif /* not lint */ 46 47 /* 48 * Phase of the Moon. Calculates the current phase of the moon. 49 * Based on routines from `Practical Astronomy with Your Calculator', 50 * by Duffett-Smith. Comments give the section from the book that 51 * particular piece of code was adapted from. 52 * 53 * -- Keith E. Brandt VIII 1984 54 * 55 */ 56 57 #include <sys/time.h> 58 #include <stdio.h> 59 #include <tzfile.h> 60 #include <math.h> 61 62 #define PI 3.141592654 63 #define EPOCH 85 64 #define EPSILONg 279.611371 /* solar ecliptic long at EPOCH */ 65 #define RHOg 282.680403 /* solar ecliptic long of perigee at EPOCH */ 66 #define ECCEN 0.01671542 /* solar orbit eccentricity */ 67 #define lzero 18.251907 /* lunar mean long at EPOCH */ 68 #define Pzero 192.917585 /* lunar mean long of perigee at EPOCH */ 69 #define Nzero 55.204723 /* lunar mean long of node at EPOCH */ 70 71 double dtor(), potm(), adj360(); 72 73 main() 74 { 75 extern int errno; 76 struct timeval tp; 77 struct timezone tzp; 78 struct tm *GMT, *gmtime(); 79 double days, today, tomorrow; 80 int cnt; 81 char *strerror(); 82 83 if (gettimeofday(&tp,&tzp)) { 84 (void)fprintf(stderr, "pom: %s\n", strerror(errno)); 85 exit(1); 86 } 87 GMT = gmtime(&tp.tv_sec); 88 days = (GMT->tm_yday + 1) + ((GMT->tm_hour + 89 (GMT->tm_min / 60.0) + (GMT->tm_sec / 3600.0)) / 24.0); 90 for (cnt = EPOCH; cnt < GMT->tm_year; ++cnt) 91 days += isleap(cnt) ? 366 : 365; 92 today = potm(days) + .5; 93 (void)printf("The Moon is "); 94 if ((int)today == 100) 95 (void)printf("Full\n"); 96 else if (!(int)today) 97 (void)printf("New\n"); 98 else { 99 tomorrow = potm(days + 1); 100 if ((int)today == 50) 101 (void)printf("%s\n", tomorrow > today ? 102 "at the First Quarter" : "at the Last Quarter"); 103 else { 104 (void)printf("%s ", tomorrow > today ? 105 "Waxing" : "Waning"); 106 if (today > 50) 107 (void)printf("Gibbous (%1.0f%% of Full)\n", 108 today); 109 else if (today < 50) 110 (void)printf("Crescent (%1.0f%% of Full)\n", 111 today); 112 } 113 } 114 } 115 116 /* 117 * potm -- 118 * return phase of the moon 119 */ 120 double 121 potm(days) 122 double days; 123 { 124 double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime; 125 double A4, lprime, V, ldprime, D, Nm; 126 127 N = 360 * days / 365.2422; /* sec 42 #3 */ 128 adj360(&N); 129 Msol = N + EPSILONg - RHOg; /* sec 42 #4 */ 130 adj360(&Msol); 131 Ec = 360 / PI * ECCEN * sin(dtor(Msol)); /* sec 42 #5 */ 132 LambdaSol = N + Ec + EPSILONg; /* sec 42 #6 */ 133 adj360(&LambdaSol); 134 l = 13.1763966 * days + lzero; /* sec 61 #4 */ 135 adj360(&l); 136 Mm = l - (0.1114041 * days) - Pzero; /* sec 61 #5 */ 137 adj360(&Mm); 138 Nm = Nzero - (0.0529539 * days); /* sec 61 #6 */ 139 adj360(&Nm); 140 Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm)); /* sec 61 #7 */ 141 Ac = 0.1858 * sin(dtor(Msol)); /* sec 61 #8 */ 142 A3 = 0.37 * sin(dtor(Msol)); 143 Mmprime = Mm + Ev - Ac - A3; /* sec 61 #9 */ 144 Ec = 6.2886 * sin(dtor(Mmprime)); /* sec 61 #10 */ 145 A4 = 0.214 * sin(dtor(2 * Mmprime)); /* sec 61 #11 */ 146 lprime = l + Ev + Ec - Ac + A4; /* sec 61 #12 */ 147 V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol))); /* sec 61 #13 */ 148 ldprime = lprime + V; /* sec 61 #14 */ 149 D = ldprime - LambdaSol; /* sec 63 #2 */ 150 return(50 * (1 - cos(dtor(D)))); /* sec 63 #3 */ 151 } 152 153 /* 154 * dtor -- 155 * convert degrees to radians 156 */ 157 double 158 dtor(deg) 159 double deg; 160 { 161 return(deg * PI / 180); 162 } 163 164 /* 165 * adj360 -- 166 * adjust value so 0 <= deg <= 360 167 */ 168 double 169 adj360(deg) 170 double *deg; 171 { 172 for (;;) 173 if (*deg < 0) 174 *deg += 360; 175 else if (*deg > 360) 176 *deg -= 360; 177 else 178 break; 179 } 180
Indexes created Thu Oct 02 01:09:59 GMT 2025