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 * @(#) Copyright (c) 1989, 1993 The Regents of the University of California. All rights reserved. 36 * @(#)pom.c 8.1 (Berkeley) 5/31/93 37 * $FreeBSD: src/games/pom/pom.c,v 1.9 1999/11/30 03:49:09 billf Exp $ 38 * $DragonFly: src/games/pom/pom.c,v 1.3 2003/11/12 14:53:54 eirikn Exp $ 39 */ 40 41 /* 42 * Phase of the Moon. Calculates the current phase of the moon. 43 * Based on routines from `Practical Astronomy with Your Calculator', 44 * by Duffett-Smith. Comments give the section from the book that 45 * particular piece of code was adapted from. 46 * 47 * -- Keith E. Brandt VIII 1984 48 * 49 */ 50 51 #include <time.h> 52 #include <stdio.h> 53 #include <math.h> 54 55 #ifndef PI 56 #define PI 3.14159265358979323846 57 #endif 58 #define EPOCH 85 59 #define EPSILONg 279.611371 /* solar ecliptic long at EPOCH */ 60 #define RHOg 282.680403 /* solar ecliptic long of perigee at EPOCH */ 61 #define ECCEN 0.01671542 /* solar orbit eccentricity */ 62 #define lzero 18.251907 /* lunar mean long at EPOCH */ 63 #define Pzero 192.917585 /* lunar mean long of perigee at EPOCH */ 64 #define Nzero 55.204723 /* lunar mean long of node at EPOCH */ 65 #define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0) 66 67 static void adj360 (double *); 68 static double dtor (double); 69 static double potm (double); 70 71 int 72 main() 73 { 74 time_t tt; 75 struct tm *GMT; 76 double days, today, tomorrow; 77 int cnt; 78 79 (void) time(&tt); 80 GMT = gmtime(&tt); 81 days = (GMT->tm_yday + 1) + ((GMT->tm_hour + 82 (GMT->tm_min / 60.0) + (GMT->tm_sec / 3600.0)) / 24.0); 83 for (cnt = EPOCH; cnt < GMT->tm_year; ++cnt) 84 days += isleap(1900 + cnt) ? 366 : 365; 85 today = potm(days) + .5; 86 (void)printf("The Moon is "); 87 if ((int)today == 100) 88 (void)printf("Full\n"); 89 else if (!(int)today) 90 (void)printf("New\n"); 91 else { 92 tomorrow = potm(days + 1); 93 if ((int)today == 50) 94 (void)printf("%s\n", tomorrow > today ? 95 "at the First Quarter" : "at the Last Quarter"); 96 else { 97 (void)printf("%s ", tomorrow > today ? 98 "Waxing" : "Waning"); 99 if (today > 50) 100 (void)printf("Gibbous (%1.0f%% of Full)\n", 101 today); 102 else if (today < 50) 103 (void)printf("Crescent (%1.0f%% of Full)\n", 104 today); 105 } 106 } 107 108 return 0; 109 } 110 111 /* 112 * potm -- 113 * return phase of the moon 114 */ 115 static double 116 potm(days) 117 double days; 118 { 119 double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime; 120 double A4, lprime, V, ldprime, D, Nm; 121 122 N = 360 * days / 365.2422; /* sec 42 #3 */ 123 adj360(&N); 124 Msol = N + EPSILONg - RHOg; /* sec 42 #4 */ 125 adj360(&Msol); 126 Ec = 360 / PI * ECCEN * sin(dtor(Msol)); /* sec 42 #5 */ 127 LambdaSol = N + Ec + EPSILONg; /* sec 42 #6 */ 128 adj360(&LambdaSol); 129 l = 13.1763966 * days + lzero; /* sec 61 #4 */ 130 adj360(&l); 131 Mm = l - (0.1114041 * days) - Pzero; /* sec 61 #5 */ 132 adj360(&Mm); 133 Nm = Nzero - (0.0529539 * days); /* sec 61 #6 */ 134 adj360(&Nm); 135 Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm)); /* sec 61 #7 */ 136 Ac = 0.1858 * sin(dtor(Msol)); /* sec 61 #8 */ 137 A3 = 0.37 * sin(dtor(Msol)); 138 Mmprime = Mm + Ev - Ac - A3; /* sec 61 #9 */ 139 Ec = 6.2886 * sin(dtor(Mmprime)); /* sec 61 #10 */ 140 A4 = 0.214 * sin(dtor(2 * Mmprime)); /* sec 61 #11 */ 141 lprime = l + Ev + Ec - Ac + A4; /* sec 61 #12 */ 142 V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol))); /* sec 61 #13 */ 143 ldprime = lprime + V; /* sec 61 #14 */ 144 D = ldprime - LambdaSol; /* sec 63 #2 */ 145 return(50 * (1 - cos(dtor(D)))); /* sec 63 #3 */ 146 } 147 148 /* 149 * dtor -- 150 * convert degrees to radians 151 */ 152 static double 153 dtor(deg) 154 double deg; 155 { 156 return(deg * PI / 180); 157 } 158 159 /* 160 * adj360 -- 161 * adjust value so 0 <= deg <= 360 162 */ 163 static void 164 adj360(deg) 165 double *deg; 166 { 167 for (;;) 168 if (*deg < 0) 169 *deg += 360; 170 else if (*deg > 360) 171 *deg -= 360; 172 else 173 break; 174 } 175