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// C++ program calculating the sunrise and sunset for// the
current date and a fixed location(latitude,longitude)// Jarmo Lammi
1999 - 2000// Last update January 6th, 2000
#include #include #include
#define pi 3.14159
//extern double pi;double tpi = 2 * pi;double degs =
180.0/pi;double rads = pi/180.0;
double L,g,daylen;double SunDia = 0.53; // Sunradius degrees
double AirRefr = 34.0/60.0; // athmospheric refraction degrees
//
// Get the days to J2000// h is UT in decimal hours// FNday only
works between 1901 to 2099 - see Meeus chapter 7
double FNday (int y, int m, int d, float h) {int luku = - 7 * (y
+ (m + 9)/12)/4 + 275*m/9 + d;// type casting necessary on PC DOS
and TClite to avoid overflowluku+= (long int)y*367;return
(double)luku - 730531.5 + h/24.0;};
// the function below returns an angle in the range// 0 to
2*pi
double FNrange (double x) { double b = x / tpi;
double a = tpi * (b - (long)(b)); if (a < 0) a =
tpi + a; return a;};
// Calculating the hourangle//double f0(double lat, double
declin) {double fo,dfo;// Correction: different sign at S HSdfo =
rads*(0.5*SunDia + AirRefr); if (lat < 0.0) dfo = -dfo;fo =
tan(declin + dfo) * tan(lat*rads);if (fo>0.99999) fo=1.0; // to
avoid overflow //
fo = asin(fo) + pi/2.0;return fo;};
// Calculating the hourangle for twilight times//double
f1(double lat, double declin) {double fi,df1;// Correction:
different sign at S HSdf1 = rads * 6.0; if (lat < 0.0) df1 =
-df1;
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fi = tan(declin + df1) * tan(lat*rads);if (fi>0.99999)
fi=1.0; // to avoid overflow //fi = asin(fi) + pi/2.0;return
fi;};
// Find the ecliptic longitude of the Sun
double FNsun (double d) {
// mean longitude of the Sun
L = FNrange(280.461 * rads + .9856474 * rads * d);
// mean anomaly of the Sun
g = FNrange(357.528 * rads + .9856003 * rads * d);
// Ecliptic longitude of the Sun
return FNrange(L + 1.915 * rads * sin(g) + .02 * rads * sin(2 *
g));};
// Display decimal hours in hours and minutesvoid
showhrmn(double dhr) {int hr,mn;hr=(int) dhr;mn = (dhr - (double)
hr)*60;if (hr < 10) cout
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double tzone=2.0;cout > latit;cin >> longit;cin
>> tzone;
// testing// m=6; day=10;
double d = FNday(y, m, day, h);
// Use FNsun to find the ecliptic longitude of the// Sun
double lambda = FNsun(d);
// Obliquity of the ecliptic
double obliq = 23.439 * rads - .0000004 * rads * d;
// Find the RA and DEC of the Sun
double alpha = atan2(cos(obliq) * sin(lambda),
cos(lambda));double delta = asin(sin(obliq) * sin(lambda));
// Find the Equation of Time// in minutes// Correction suggested
by David Smithdouble LL = L - alpha;if (L < pi) LL += tpi;double
equation = 1440.0 * (1.0 - LL / tpi);double ha =
f0(latit,delta);double hb = f1(latit,delta);double twx = hb - ha;
// length of twilight in radianstwx = 12.0*twx/pi; // length of
twilight in hourscout
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cout
