178 lines
5.4 KiB
C
178 lines
5.4 KiB
C
/*
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* Copyright (c) 1989, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software posted to USENET.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef lint
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static const char copyright[] =
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"@(#) Copyright (c) 1989, 1993\n\
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The Regents of the University of California. All rights reserved.\n";
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#endif /* not lint */
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#ifndef lint
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static const char sccsid[] = "@(#)pom.c 8.1 (Berkeley) 5/31/93";
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#endif /* not lint */
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/*
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* Phase of the Moon. Calculates the current phase of the moon.
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* Based on routines from `Practical Astronomy with Your Calculator',
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* by Duffett-Smith. Comments give the section from the book that
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* particular piece of code was adapted from.
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*
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* -- Keith E. Brandt VIII 1984
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*
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*/
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#include <time.h>
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#include <stdio.h>
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#include <math.h>
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#define PI 3.141592654
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#define EPOCH 85
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#define EPSILONg 279.611371 /* solar ecliptic long at EPOCH */
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#define RHOg 282.680403 /* solar ecliptic long of perigee at EPOCH */
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#define ECCEN 0.01671542 /* solar orbit eccentricity */
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#define lzero 18.251907 /* lunar mean long at EPOCH */
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#define Pzero 192.917585 /* lunar mean long of perigee at EPOCH */
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#define Nzero 55.204723 /* lunar mean long of node at EPOCH */
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#define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0)
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static void adj360 __P((double *));
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static double dtor __P((double));
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static double potm __P((double));
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int
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main()
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{
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time_t tt;
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struct tm *GMT;
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double days, today, tomorrow;
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int cnt;
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(void) time(&tt);
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GMT = gmtime(&tt);
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days = (GMT->tm_yday + 1) + ((GMT->tm_hour +
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(GMT->tm_min / 60.0) + (GMT->tm_sec / 3600.0)) / 24.0);
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for (cnt = EPOCH; cnt < GMT->tm_year; ++cnt)
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days += isleap(1900 + cnt) ? 366 : 365;
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today = potm(days) + .5;
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(void)printf("The Moon is ");
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if ((int)today == 100)
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(void)printf("Full\n");
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else if (!(int)today)
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(void)printf("New\n");
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else {
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tomorrow = potm(days + 1);
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if ((int)today == 50)
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(void)printf("%s\n", tomorrow > today ?
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"at the First Quarter" : "at the Last Quarter");
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else {
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(void)printf("%s ", tomorrow > today ?
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"Waxing" : "Waning");
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if (today > 50)
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(void)printf("Gibbous (%1.0f%% of Full)\n",
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today);
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else if (today < 50)
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(void)printf("Crescent (%1.0f%% of Full)\n",
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today);
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}
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}
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return 0;
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}
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/*
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* potm --
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* return phase of the moon
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*/
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static double
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potm(days)
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double days;
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{
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double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime;
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double A4, lprime, V, ldprime, D, Nm;
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N = 360 * days / 365.2422; /* sec 42 #3 */
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adj360(&N);
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Msol = N + EPSILONg - RHOg; /* sec 42 #4 */
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adj360(&Msol);
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Ec = 360 / PI * ECCEN * sin(dtor(Msol)); /* sec 42 #5 */
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LambdaSol = N + Ec + EPSILONg; /* sec 42 #6 */
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adj360(&LambdaSol);
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l = 13.1763966 * days + lzero; /* sec 61 #4 */
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adj360(&l);
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Mm = l - (0.1114041 * days) - Pzero; /* sec 61 #5 */
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adj360(&Mm);
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Nm = Nzero - (0.0529539 * days); /* sec 61 #6 */
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adj360(&Nm);
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Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm)); /* sec 61 #7 */
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Ac = 0.1858 * sin(dtor(Msol)); /* sec 61 #8 */
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A3 = 0.37 * sin(dtor(Msol));
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Mmprime = Mm + Ev - Ac - A3; /* sec 61 #9 */
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Ec = 6.2886 * sin(dtor(Mmprime)); /* sec 61 #10 */
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A4 = 0.214 * sin(dtor(2 * Mmprime)); /* sec 61 #11 */
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lprime = l + Ev + Ec - Ac + A4; /* sec 61 #12 */
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V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol))); /* sec 61 #13 */
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ldprime = lprime + V; /* sec 61 #14 */
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D = ldprime - LambdaSol; /* sec 63 #2 */
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return(50 * (1 - cos(dtor(D)))); /* sec 63 #3 */
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}
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/*
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* dtor --
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* convert degrees to radians
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*/
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static double
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dtor(deg)
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double deg;
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{
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return(deg * PI / 180);
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}
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/*
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* adj360 --
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* adjust value so 0 <= deg <= 360
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*/
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static void
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adj360(deg)
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double *deg;
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{
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for (;;)
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if (*deg < 0)
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*deg += 360;
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else if (*deg > 360)
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*deg -= 360;
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else
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break;
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}
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