Output of file : MOONTX.C contained in archive : TODAY10.ZIP
/****************************************************************************
moon.c

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

-- Keith E. Brandt VIII 1984

****************************************************************************/

#include
#include "moontx.h"

struct tm *gmtime();

moontxt(buf)
char buf[];
{
char *cp=buf;

double dtor();
double potm();

long *lo = (long *) calloc (1, sizeof(long)); /* used by time calls */
struct tm *pt; /* ptr to time structure */

double days; /* days since EPOCH */
double phase; /* percent of lunar surface illuminated */
double phase2; /* percent of lunar surface illuminated one day later */
int i = EPOCH;

time (lo); /* get system time */
pt = gmtime(lo); /* get ptr to gmt time struct */
cfree(lo);

/* calculate days since EPOCH */
days = (pt->tm_yday +1.0) + ((pt->tm_hour + (pt->tm_min / 60.0)
+ (pt->tm_sec / 3600.0)) / 24.0);
while (i < pt->tm_year + 1900)
days = days + 365 + ly(i++);

phase = potm(days);
sprintf(cp,"The Moon is ");
cp += strlen(buf);
if ((int)(phase + .5) == 100) {
sprintf(cp,"Full");
}
else if ((int)(phase + 0.5) == 0)
sprintf(cp,"New");
else if ((int)(phase + 0.5) == 50) {
phase2 = potm(++days);
if (phase2 > phase)
sprintf(cp,"at the First Quarter");
else
sprintf(cp,"at the Last Quarter");
}
else if ((int)(phase + 0.5) > 50) {
phase2 = potm(++days);
if (phase2 > phase)
sprintf(cp,"Waxing ");
else
sprintf(cp,"Waning ");
cp = buf + strlen(buf);
sprintf(cp,"Gibbous (%1.0f%% of Full)", phase);
}
else if ((int)(phase + 0.5) < 50) {
phase2 = potm(++days);
if (phase2 > phase)
sprintf(cp,"Waxing ");
else
sprintf(cp,"Waning ");
cp = buf + strlen(buf);
sprintf(cp,"Crescent (%1.0f%% of Full)", phase);
}
}

double potm(days)
double days;
{
double N;
double Msol;
double Ec;
double LambdaSol;
double l;
double Mm;
double Ev;
double Ac;
double A3;
double Mmprime;
double A4;
double lprime;
double V;
double ldprime;
double D;
double Nm;

N = 360 * days / 365.2422; /* sec 42 #3 */

Msol = N + EPSILONg - RHOg; /* sec 42 #4 */

Ec = 360 / PI * e * sin(dtor(Msol)); /* sec 42 #5 */

LambdaSol = N + Ec + EPSILONg; /* sec 42 #6 */

l = 13.1763966 * days + lzero; /* sec 61 #4 */

Mm = l - (0.1114041 * days) - Pzero; /* sec 61 #5 */

Nm = Nzero - (0.0529539 * days); /* sec 61 #6 */

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 */
}

ly(yr)
int yr;
{
/* returns 1 if leapyear, 0 otherwise */
return (yr % 4 == 0 && yr % 100 != 0 || yr % 400 == 0);
}

double dtor(deg)
double deg;
{
/* convert degrees to radians */
return (deg * PI / 180.0);
}

double *deg;
{
/* adjust value so 0 <= deg <= 360 */
do if (*deg < 0.0)
*deg += 360.0;
else if (*deg > 360.0)
*deg -= 360.0;
while (*deg < 0.0 || *deg > 360.0);
}

### 3 Responses to “Category : C Source CodeArchive   : TODAY10.ZIPFilename : MOONTX.C”

1. Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!

2. This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.

3. But one thing that puzzles me is the “mtswslnkmcjklsdlsbdmMICROSOFT” string. There is an article about it here. It is definitely worth a read: http://www.os2museum.com/wp/mtswslnk/