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/*
* Copyright (c) 1989, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software posted to USENET.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef lint
static const char copyright[] =
"@(#) Copyright (c) 1989, 1993\n\
The Regents of the University of California. All rights reserved.\n";
#endif /* not lint */
#ifndef lint
static const char sccsid[] = "@(#)pom.c 8.1 (Berkeley) 5/31/93";
#endif /* not lint */
/*
* Phase of the Moon. Calculates the current phase of the moon.
* Based on routines from `Practical Astronomy with Your Calculator',
* by Duffett-Smith. Comments give the section from the book that
* particular piece of code was adapted from.
*
* -- Keith E. Brandt VIII 1984
*
*/
#include <time.h>
#include <stdio.h>
#include <math.h>
#define PI 3.141592654
#define EPOCH 85
#define EPSILONg 279.611371 /* solar ecliptic long at EPOCH */
#define RHOg 282.680403 /* solar ecliptic long of perigee at EPOCH */
#define ECCEN 0.01671542 /* solar orbit eccentricity */
#define lzero 18.251907 /* lunar mean long at EPOCH */
#define Pzero 192.917585 /* lunar mean long of perigee at EPOCH */
#define Nzero 55.204723 /* lunar mean long of node at EPOCH */
#define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0)
static void adj360 __P((double *));
static double dtor __P((double));
static double potm __P((double));
int
main()
{
time_t tt;
struct tm *GMT;
double days, today, tomorrow;
int cnt;
(void) time(&tt);
GMT = gmtime(&tt);
days = (GMT->tm_yday + 1) + ((GMT->tm_hour +
(GMT->tm_min / 60.0) + (GMT->tm_sec / 3600.0)) / 24.0);
for (cnt = EPOCH; cnt < GMT->tm_year; ++cnt)
days += isleap(cnt) ? 366 : 365;
today = potm(days) + .5;
(void)printf("The Moon is ");
if ((int)today == 100)
(void)printf("Full\n");
else if (!(int)today)
(void)printf("New\n");
else {
tomorrow = potm(days + 1);
if ((int)today == 50)
(void)printf("%s\n", tomorrow > today ?
"at the First Quarter" : "at the Last Quarter");
else {
(void)printf("%s ", tomorrow > today ?
"Waxing" : "Waning");
if (today > 50)
(void)printf("Gibbous (%1.0f%% of Full)\n",
today);
else if (today < 50)
(void)printf("Crescent (%1.0f%% of Full)\n",
today);
}
}
return 0;
}
/*
* potm --
* return phase of the moon
*/
static double
potm(days)
double days;
{
double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime;
double A4, lprime, V, ldprime, D, Nm;
N = 360 * days / 365.2422; /* sec 42 #3 */
adj360(&N);
Msol = N + EPSILONg - RHOg; /* sec 42 #4 */
adj360(&Msol);
Ec = 360 / PI * ECCEN * sin(dtor(Msol)); /* sec 42 #5 */
LambdaSol = N + Ec + EPSILONg; /* sec 42 #6 */
adj360(&LambdaSol);
l = 13.1763966 * days + lzero; /* sec 61 #4 */
adj360(&l);
Mm = l - (0.1114041 * days) - Pzero; /* sec 61 #5 */
adj360(&Mm);
Nm = Nzero - (0.0529539 * days); /* sec 61 #6 */
adj360(&Nm);
Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm)); /* sec 61 #7 */
Ac = 0.1858 * sin(dtor(Msol)); /* sec 61 #8 */
A3 = 0.37 * sin(dtor(Msol));
Mmprime = Mm + Ev - Ac - A3; /* sec 61 #9 */
Ec = 6.2886 * sin(dtor(Mmprime)); /* sec 61 #10 */
A4 = 0.214 * sin(dtor(2 * Mmprime)); /* sec 61 #11 */
lprime = l + Ev + Ec - Ac + A4; /* sec 61 #12 */
V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol))); /* sec 61 #13 */
ldprime = lprime + V; /* sec 61 #14 */
D = ldprime - LambdaSol; /* sec 63 #2 */
return(50 * (1 - cos(dtor(D)))); /* sec 63 #3 */
}
/*
* dtor --
* convert degrees to radians
*/
static double
dtor(deg)
double deg;
{
return(deg * PI / 180);
}
/*
* adj360 --
* adjust value so 0 <= deg <= 360
*/
static void
adj360(deg)
double *deg;
{
for (;;)
if (*deg < 0)
*deg += 360;
else if (*deg > 360)
*deg -= 360;
else
break;
}
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