double calcSunEqOfCenter(double t)
{
double m = calcGeomMeanAnomalySun(t);
double mrad = degToRad(m);
double sinm = sin(mrad);
double sin2m = sin(mrad+mrad);
double sin3m = sin(mrad+mrad+mrad);
double C = sinm * (1.914602 - t * (0.004817 + 0.000014 * t)) + sin2m * (0.019993 - 0.000101 * t) + sin3m * 0.000289;
return C; // 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 equation of center for the sun (degrees) */
double calcSunEqOfCenter(double t) {
double m = deg2rad(calcGeomMeanAnomalySun(t));
return sin(m) * (1.914602 - t * (0.004817 + 0.000014 * t)) + sin(m+m) * (0.019993 - 0.000101 * t) + sin(m+m+m) * 0.000289;
}
