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 1.4 2006/08/08 17:08:49 pavalos 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 #define EPOCH 85 56 #define EPSILONg 279.611371 /* solar ecliptic long at EPOCH */ 57 #define RHOg 282.680403 /* solar ecliptic long of perigee at EPOCH */ 58 #define ECCEN 0.01671542 /* solar orbit eccentricity */ 59 #define lzero 18.251907 /* lunar mean long at EPOCH */ 60 #define Pzero 192.917585 /* lunar mean long of perigee at EPOCH */ 61 #define Nzero 55.204723 /* lunar mean long of node at EPOCH */ 62 #define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0) 63 64 static void adj360 (double *); 65 static double dtor (double); 66 static double potm (double); 67 68 int 69 main(void) 70 { 71 time_t tt; 72 struct tm *GMT; 73 double days, today, tomorrow; 74 int cnt; 75 76 (void) time(&tt); 77 GMT = gmtime(&tt); 78 days = (GMT->tm_yday + 1) + ((GMT->tm_hour + 79 (GMT->tm_min / 60.0) + (GMT->tm_sec / 3600.0)) / 24.0); 80 for (cnt = EPOCH; cnt < GMT->tm_year; ++cnt) 81 days += isleap(1900 + cnt) ? 366 : 365; 82 today = potm(days) + .5; 83 (void)printf("The Moon is "); 84 if ((int)today == 100) 85 (void)printf("Full\n"); 86 else if (!(int)today) 87 (void)printf("New\n"); 88 else { 89 tomorrow = potm(days + 1); 90 if ((int)today == 50) 91 (void)printf("%s\n", tomorrow > today ? 92 "at the First Quarter" : "at the Last Quarter"); 93 else { 94 (void)printf("%s ", tomorrow > today ? 95 "Waxing" : "Waning"); 96 if (today > 50) 97 (void)printf("Gibbous (%1.0f%% of Full)\n", 98 today); 99 else if (today < 50) 100 (void)printf("Crescent (%1.0f%% of Full)\n", 101 today); 102 } 103 } 104 105 return 0; 106 } 107 108 /* 109 * potm -- 110 * return phase of the moon 111 */ 112 static double 113 potm(double days) 114 { 115 double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime; 116 double A4, lprime, V, ldprime, D, Nm; 117 118 N = 360 * days / 365.2422; /* sec 42 #3 */ 119 adj360(&N); 120 Msol = N + EPSILONg - RHOg; /* sec 42 #4 */ 121 adj360(&Msol); 122 Ec = 360 / M_PI * ECCEN * sin(dtor(Msol)); /* sec 42 #5 */ 123 LambdaSol = N + Ec + EPSILONg; /* sec 42 #6 */ 124 adj360(&LambdaSol); 125 l = 13.1763966 * days + lzero; /* sec 61 #4 */ 126 adj360(&l); 127 Mm = l - (0.1114041 * days) - Pzero; /* sec 61 #5 */ 128 adj360(&Mm); 129 Nm = Nzero - (0.0529539 * days); /* sec 61 #6 */ 130 adj360(&Nm); 131 Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm)); /* sec 61 #7 */ 132 Ac = 0.1858 * sin(dtor(Msol)); /* sec 61 #8 */ 133 A3 = 0.37 * sin(dtor(Msol)); 134 Mmprime = Mm + Ev - Ac - A3; /* sec 61 #9 */ 135 Ec = 6.2886 * sin(dtor(Mmprime)); /* sec 61 #10 */ 136 A4 = 0.214 * sin(dtor(2 * Mmprime)); /* sec 61 #11 */ 137 lprime = l + Ev + Ec - Ac + A4; /* sec 61 #12 */ 138 V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol))); /* sec 61 #13 */ 139 ldprime = lprime + V; /* sec 61 #14 */ 140 D = ldprime - LambdaSol; /* sec 63 #2 */ 141 return(50 * (1 - cos(dtor(D)))); /* sec 63 #3 */ 142 } 143 144 /* 145 * dtor -- 146 * convert degrees to radians 147 */ 148 static double 149 dtor(double deg) 150 { 151 return(deg * M_PI / 180); 152 } 153 154 /* 155 * adj360 -- 156 * adjust value so 0 <= deg <= 360 157 */ 158 static void 159 adj360(double *deg) 160 { 161 for (;;) 162 if (*deg < 0) 163 *deg += 360; 164 else if (*deg > 360) 165 *deg -= 360; 166 else 167 break; 168 } 169