static double sun_ecliptic_long ( double t )
{
// Returns ecliptic longitude of the Sun in radians
// given the fraction of a Julian century from J2000.0
double dr = M_PI / 180.0 ;
return( sun_mean_longitude( t ) +
(1.915 * sin ( sun_mean_anomaly( t ) ) +
0.020 * sin ( 2.0 * sun_mean_anomaly( t ) ) ) * dr );
}
void calculate_eot_and_sun_rise_transit_set(spa_data *spa)
{
spa_data sun_rts;
double nu, m, h0, n;
double alpha[JD_COUNT], delta[JD_COUNT];
double m_rts[SUN_COUNT], nu_rts[SUN_COUNT], h_rts[SUN_COUNT];
double alpha_prime[SUN_COUNT], delta_prime[SUN_COUNT], h_prime[SUN_COUNT];
double h0_prime = -1*(SUN_RADIUS + spa->atmos_refract);
int i;
sun_rts = *spa;
m = sun_mean_longitude(spa->jme);
spa->eot = eot(m, spa->alpha, spa->del_psi, spa->epsilon);
sun_rts.hour = sun_rts.minute = sun_rts.second = 0;
sun_rts.timezone = 0.0;
sun_rts.jd = julian_day (sun_rts.year, sun_rts.month, sun_rts.day,
sun_rts.hour, sun_rts.minute, sun_rts.second, sun_rts.timezone);
calculate_geocentric_sun_right_ascension_and_declination(&sun_rts);
nu = sun_rts.nu;
sun_rts.delta_t = 0;
sun_rts.jd--;
for (i = 0; i < JD_COUNT; i++) {
calculate_geocentric_sun_right_ascension_and_declination(&sun_rts);
alpha[i] = sun_rts.alpha;
delta[i] = sun_rts.delta;
sun_rts.jd++;
}
m_rts[SUN_TRANSIT] = approx_sun_transit_time(alpha[JD_ZERO], spa->longitude, nu);
h0 = sun_hour_angle_at_rise_set(spa->latitude, delta[JD_ZERO], h0_prime);
if (h0 >= 0) {
approx_sun_rise_and_set(m_rts, h0);
for (i = 0; i < SUN_COUNT; i++) {
nu_rts[i] = nu + 360.985647*m_rts[i];
n = m_rts[i] + spa->delta_t/86400.0;
alpha_prime[i] = rts_alpha_delta_prime(alpha, n);
delta_prime[i] = rts_alpha_delta_prime(delta, n);
h_prime[i] = limit_degrees180pm(nu_rts[i] + spa->longitude - alpha_prime[i]);
h_rts[i] = rts_sun_altitude(spa->latitude, delta_prime[i], h_prime[i]);
}
spa->srha = h_prime[SUN_RISE];
spa->ssha = h_prime[SUN_SET];
spa->sta = h_rts[SUN_TRANSIT];
spa->suntransit = dayfrac_to_local_hr(m_rts[SUN_TRANSIT] - h_prime[SUN_TRANSIT] / 360.0,
spa->timezone);
spa->sunrise = dayfrac_to_local_hr(sun_rise_and_set(m_rts, h_rts, delta_prime,
spa->latitude, h_prime, h0_prime, SUN_RISE), spa->timezone);
spa->sunset = dayfrac_to_local_hr(sun_rise_and_set(m_rts, h_rts, delta_prime,
spa->latitude, h_prime, h0_prime, SUN_SET), spa->timezone);
} else spa->srha= spa->ssha= spa->sta= spa->suntransit= spa->sunrise= spa->sunset= -99999;
}
