double calcSunDeclination(double t)
{
double e = calcObliquityCorrection(t);
double lambda = calcSunApparentLong(t);
double sint = sin(degToRad(e)) * sin(degToRad(lambda));
double theta = radToDeg(asin(sint));
return theta; // in degrees
}
/* Purpose: calculate the difference between true solar time and mean
* solar time (minutes)
*/
double calcEquationOfTime(double t) {
double l0 = deg2rad(calcGeomMeanLongSun(t));
double e = calcEccentricityEarthOrbit(t);
double m = deg2rad(calcGeomMeanAnomalySun(t));
double y = tan(deg2rad(calcObliquityCorrection(t))/2.0);
double sinm = sin(m);
y *= y;
return rad2deg(y*sin(2.0*l0) - 2.0*e*sinm + 4.0*e*y*sinm*cos(2.0*l0)
- 0.5*y*y*sin(4.0*l0) - 1.25*e*e*sin(2.0*m))*4.0;
}
static double calcEquationOfTime(
double t) {
double epsilon = calcObliquityCorrection(t);
double l0 = calcGeomMeanLongSun(t);
double e = calcEccentricityEarthOrbit(t);
double m = calcGeomMeanAnomalySun(t);
double y = tan(degToRad(epsilon) / 2.0);
y *= y;
double sin2l0 = sin(2.0 * degToRad(l0));
double sinm = sin(degToRad(m));
double cos2l0 = cos(2.0 * degToRad(l0));
double sin4l0 = sin(4.0 * degToRad(l0));
double sin2m = sin(2.0 * degToRad(m));
double Etime = y * sin2l0 - 2.0 * e * sinm + 4.0 * e * y * sinm * cos2l0 - 0.5 * y * y * sin4l0 - 1.25 * e * e * sin2m;
return radToDeg(Etime) * 4.0; // in minutes of time
}
/* Purpose: calculate the declination of the sun (degrees) */
double calcSunDeclination(double t) {
return rad2deg(asin(sin(deg2rad(calcObliquityCorrection(t))) *
sin(deg2rad(calcSunApparentLong(t)))));
}
