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[] = "@(#)pom.c 5.3 (Berkeley) 2/28/91";
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
70 double dtor(), potm(), adj360();
71
main()72 main()
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 */
119 double
potm(days)120 potm(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 */
156 double
dtor(deg)157 dtor(deg)
158 double deg;
159 {
160 return(deg * PI / 180);
161 }
162
163 /*
164 * adj360 --
165 * adjust value so 0 <= deg <= 360
166 */
167 double
adj360(deg)168 adj360(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