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. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * @(#) Copyright (c) 1989, 1993 The Regents of the University of California. All rights reserved. 32 * @(#)pom.c 8.1 (Berkeley) 5/31/93 33 * $FreeBSD: src/games/pom/pom.c,v 1.9 1999/11/30 03:49:09 billf Exp $ 34 * $DragonFly: src/games/pom/pom.c,v 1.4 2006/08/08 17:08:49 pavalos Exp $ 35 */ 36 37 /* 38 * Phase of the Moon. Calculates the current phase of the moon. 39 * Based on routines from `Practical Astronomy with Your Calculator', 40 * by Duffett-Smith. Comments give the section from the book that 41 * particular piece of code was adapted from. 42 * 43 * -- Keith E. Brandt VIII 1984 44 * 45 */ 46 47 #include <time.h> 48 #include <stdio.h> 49 #include <math.h> 50 51 #define EPOCH 85 52 #define EPSILONg 279.611371 /* solar ecliptic long at EPOCH */ 53 #define RHOg 282.680403 /* solar ecliptic long of perigee at EPOCH */ 54 #define ECCEN 0.01671542 /* solar orbit eccentricity */ 55 #define lzero 18.251907 /* lunar mean long at EPOCH */ 56 #define Pzero 192.917585 /* lunar mean long of perigee at EPOCH */ 57 #define Nzero 55.204723 /* lunar mean long of node at EPOCH */ 58 #define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0) 59 60 static void adj360 (double *); 61 static double dtor (double); 62 static double potm (double); 63 64 int 65 main(void) 66 { 67 time_t tt; 68 struct tm *GMT; 69 double days, today, tomorrow; 70 int cnt; 71 72 (void) time(&tt); 73 GMT = gmtime(&tt); 74 days = (GMT->tm_yday + 1) + ((GMT->tm_hour + 75 (GMT->tm_min / 60.0) + (GMT->tm_sec / 3600.0)) / 24.0); 76 for (cnt = EPOCH; cnt < GMT->tm_year; ++cnt) 77 days += isleap(1900 + cnt) ? 366 : 365; 78 today = potm(days) + .5; 79 (void)printf("The Moon is "); 80 if ((int)today == 100) 81 (void)printf("Full\n"); 82 else if (!(int)today) 83 (void)printf("New\n"); 84 else { 85 tomorrow = potm(days + 1); 86 if ((int)today == 50) 87 (void)printf("%s\n", tomorrow > today ? 88 "at the First Quarter" : "at the Last Quarter"); 89 else { 90 (void)printf("%s ", tomorrow > today ? 91 "Waxing" : "Waning"); 92 if (today > 50) 93 (void)printf("Gibbous (%1.0f%% of Full)\n", 94 today); 95 else if (today < 50) 96 (void)printf("Crescent (%1.0f%% of Full)\n", 97 today); 98 } 99 } 100 101 return 0; 102 } 103 104 /* 105 * potm -- 106 * return phase of the moon 107 */ 108 static double 109 potm(double days) 110 { 111 double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime; 112 double A4, lprime, V, ldprime, D, Nm; 113 114 N = 360 * days / 365.2422; /* sec 42 #3 */ 115 adj360(&N); 116 Msol = N + EPSILONg - RHOg; /* sec 42 #4 */ 117 adj360(&Msol); 118 Ec = 360 / M_PI * ECCEN * sin(dtor(Msol)); /* sec 42 #5 */ 119 LambdaSol = N + Ec + EPSILONg; /* sec 42 #6 */ 120 adj360(&LambdaSol); 121 l = 13.1763966 * days + lzero; /* sec 61 #4 */ 122 adj360(&l); 123 Mm = l - (0.1114041 * days) - Pzero; /* sec 61 #5 */ 124 adj360(&Mm); 125 Nm = Nzero - (0.0529539 * days); /* sec 61 #6 */ 126 adj360(&Nm); 127 Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm)); /* sec 61 #7 */ 128 Ac = 0.1858 * sin(dtor(Msol)); /* sec 61 #8 */ 129 A3 = 0.37 * sin(dtor(Msol)); 130 Mmprime = Mm + Ev - Ac - A3; /* sec 61 #9 */ 131 Ec = 6.2886 * sin(dtor(Mmprime)); /* sec 61 #10 */ 132 A4 = 0.214 * sin(dtor(2 * Mmprime)); /* sec 61 #11 */ 133 lprime = l + Ev + Ec - Ac + A4; /* sec 61 #12 */ 134 V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol))); /* sec 61 #13 */ 135 ldprime = lprime + V; /* sec 61 #14 */ 136 D = ldprime - LambdaSol; /* sec 63 #2 */ 137 return(50 * (1 - cos(dtor(D)))); /* sec 63 #3 */ 138 } 139 140 /* 141 * dtor -- 142 * convert degrees to radians 143 */ 144 static double 145 dtor(double deg) 146 { 147 return(deg * M_PI / 180); 148 } 149 150 /* 151 * adj360 -- 152 * adjust value so 0 <= deg <= 360 153 */ 154 static void 155 adj360(double *deg) 156 { 157 for (;;) 158 if (*deg < 0) 159 *deg += 360; 160 else if (*deg > 360) 161 *deg -= 360; 162 else 163 break; 164 } 165