void format_result(const char *format, struct object_details *result) {
char buffer[128];
char *local_format = strdup(format);
int i;
struct ln_hms ra;
/* convert results */
ln_deg_to_hms(result->equ.ra, &ra);
ln_get_hrz_from_equ(&result->equ, &result->obs, result->jd, &result->hrz);
result->azidir = ln_hrz_to_nswe(&result->hrz);
result->hrz.az = ln_range_degrees(result->hrz.az + 180);
result->hrz.alt = ln_range_degrees(result->hrz.alt);
struct specifiers specifiers[] = {
{"%J", &result->jd, DOUBLE},
{"§r", &result->equ.ra, DOUBLE},
{"§d", &result->equ.dec, DOUBLE},
{"§a", &result->hrz.az, DOUBLE},
{"§h", &result->hrz.alt, DOUBLE},
{"§d", &result->diameter, DOUBLE},
{"§e", &result->distance, DOUBLE},
{"§t", &result->tz, INTEGER},
{"§A", &result->obs.lat, DOUBLE},
{"§O", &result->obs.lng, DOUBLE},
{"§s", (void *) result->azidir, STRING},
{"§§", "§", STRING},
{0}
};
for (i = 0; specifiers[i].token; i++) {
if (strstr(local_format, specifiers[i].token) != NULL) {
switch (specifiers[i].format) {
case DOUBLE: snprintf(buffer, sizeof(buffer), "%." PRECISION "f", * (double *) specifiers[i].data); break;
case STRING: snprintf(buffer, sizeof(buffer), "%s", (char *) specifiers[i].data); break;
case INTEGER: snprintf(buffer, sizeof(buffer), "%d", * (int *) specifiers[i].data); break;
}
local_format = strreplace(local_format, specifiers[i].token, buffer);
}
}
strfjd(buffer, sizeof(buffer), local_format, result->jd, result->tz);
printf("%s\n", buffer);
free(local_format);
}
void MainWindow::setSunCurrentHeading(const QDateTime &dateTime)
{
struct ln_equ_posn equ;
struct ln_lnlat_posn observer;
struct ln_hrz_posn hpos;
double JD;
observer.lat = ui->latEdit->text().toFloat();
observer.lng = ui->lngEdit->text().toFloat();
ln_date novaDate;
novaDate.years = dateTime.date().year();
novaDate.months = dateTime.date().month();
novaDate.days = dateTime.date().day();
novaDate.hours = dateTime.time().hour();
novaDate.minutes = dateTime.time().minute();
novaDate.seconds = dateTime.time().second();
JD = ln_get_julian_day(&novaDate);
/* ra, dec */
ln_get_solar_equ_coords (JD, &equ);
ln_get_hrz_from_equ(&equ, &observer, JD, &hpos);
double a = ln_range_degrees(hpos.az - 180);
sunHeading->setHeading(a);
mc->updateRequestNew();
}
void MainWindow::setSunVectors(ln_zonedate* date, ln_lnlat_posn* observer, Vector* vector)
{
struct ln_equ_posn equ;
struct ln_hrz_posn hpos;
double JD;
ln_date lnDate;
lnDate.years = date->years;
lnDate.months = date->months;
lnDate.days = date->days;
lnDate.hours = date->hours;
lnDate.minutes = date->minutes;
lnDate.seconds = date->seconds;
JD = ln_get_julian_day(&lnDate);
/* ra, dec */
ln_get_solar_equ_coords (JD, &equ);
ln_get_hrz_from_equ(&equ, observer, JD, &hpos);
double a = ln_range_degrees(hpos.az - 180);
vector->setHeading(a);
}
/* convert degrees to hh:mm:ss */
void ln_deg_to_hms (double degrees, struct ln_hms * hms)
{
double dtemp;
degrees = ln_range_degrees (degrees);
/* divide degrees by 15 to get the hours */
dtemp = degrees / 15.0;
hms->hours = (unsigned short)dtemp;
/* multiply remainder by 60 to get minutes */
dtemp = 60*(dtemp - hms->hours);
hms->minutes = (unsigned short)dtemp;
/* multiply remainder by 60 to get seconds */
hms->seconds = 60*(dtemp - hms->minutes);
/* catch any overflows */
if (hms->seconds > 59) {
hms->seconds = 0;
hms->minutes ++;
}
if (hms->minutes > 59) {
hms->minutes = 0;
hms->hours ++;
}
}
/*! \fn double ln_get_ell_body_elong (double JD, struct ln_ell_orbit * orbit);
* \param JD Julian day
* \param orbit Orbital parameters
* \return Elongation to the Sun.
*
* Calculate the bodies elongation to the Sun..
*/
double ln_get_ell_body_elong (double JD, struct ln_ell_orbit * orbit)
{
double r,R,d;
double t;
double elong;
double E,M;
/* time since perihelion */
t = JD - orbit->JD;
/* get mean anomaly */
if (orbit->n == 0)
orbit->n = ln_get_ell_mean_motion (orbit->a);
M = ln_get_ell_mean_anomaly (orbit->n, t);
/* get eccentric anomaly */
E = ln_solve_kepler (orbit->e, M);
/* get radius vector */
r = ln_get_ell_radius_vector (orbit->a, orbit->e, E);
/* get solar and Earth-Sun distances */
R = ln_get_earth_solar_dist (JD);
d = ln_get_ell_body_solar_dist (JD, orbit);
elong = (R * R + d * d - r * r) / ( 2.0 * R * d );
return ln_range_degrees (ln_rad_to_deg (acos (elong)));
}
/*!
* \fn void ln_get_ell_body_equ_coords (double JD, struct ln_ell_orbit * orbit, struct ln_equ_posn * posn)
* \param JD Julian Day.
* \param orbit Orbital parameters.
* \param posn Pointer to hold asteroid position.
*
* Calculate a bodies equatorial coordinates for the given julian day.
*/
void ln_get_ell_body_equ_coords (double JD, struct ln_ell_orbit * orbit, struct ln_equ_posn * posn)
{
struct ln_rect_posn body_rect_posn, sol_rect_posn;
double dist, t;
double x,y,z;
/* get solar and body rect coords */
ln_get_ell_helio_rect_posn (orbit, JD, &body_rect_posn);
ln_get_solar_geo_coords (JD, &sol_rect_posn);
/* calc distance and light time */
dist = ln_get_rect_distance (&body_rect_posn, &sol_rect_posn);
t = ln_get_light_time (dist);
/* repeat calculation with new time (i.e. JD - t) */
ln_get_ell_helio_rect_posn (orbit, JD - t, &body_rect_posn);
/* calc equ coords equ 33.10 */
x = sol_rect_posn.X + body_rect_posn.X;
y = sol_rect_posn.Y + body_rect_posn.Y;
z = sol_rect_posn.Z + body_rect_posn.Z;
posn->ra = ln_range_degrees(ln_rad_to_deg(atan2 (y,x)));
posn->dec = ln_rad_to_deg(asin (z / sqrt (x * x + y * y + z * z)));
}
/* equ 30.1 */
double ln_get_ell_true_anomaly (double e, double E)
{
double v;
E = ln_deg_to_rad (E);
v = sqrt ((1.0 + e) / (1.0 - e)) * tan (E / 2.0);
v = 2.0 * atan (v);
v = ln_range_degrees (ln_rad_to_deg (v));
return v;
}
/* equ 30.1 */
double ln_get_par_true_anomaly (double q, double t)
{
double v;
double s;
s = ln_solve_barker (q,t);
v = 2.0 * atan (s);
return ln_range_degrees(ln_rad_to_deg(v));
}
void normalizeRaDec (double &ra, double &dec)
{
if (dec < -90)
{
dec = -180 - dec;
ra = ra - 180;
}
else if (dec > 90)
{
dec = 180 - dec;
ra = ra - 180;
}
ra = ln_range_degrees (ra);
}
/* Equ 20.2, 20.4 pg 126 */
void ln_get_equ_prec2 (struct ln_equ_posn * mean_position, double fromJD, double toJD, struct ln_equ_posn * position)
{
long double t, t2, t3, A, B, C, zeta, eta, theta, ra, dec, mean_ra, mean_dec, T, T2;
/* change original ra and dec to radians */
mean_ra = ln_deg_to_rad (mean_position->ra);
mean_dec = ln_deg_to_rad (mean_position->dec);
/* calc t, T, zeta, eta and theta Equ 20.2 */
T = ((long double) (fromJD - JD2000)) / 36525.0;
T *= 1.0 / 3600.0;
t = ((long double) (toJD - fromJD)) / 36525.0;
t *= 1.0 / 3600.0;
T2 = T * T;
t2 = t * t;
t3 = t2 *t;
zeta = (2306.2181 + 1.39656 * T - 0.000139 * T2) * t + (0.30188 - 0.000344 * T) * t2 + 0.017998 * t3;
eta = (2306.2181 + 1.39656 * T - 0.000139 * T2) * t + (1.09468 + 0.000066 * T) * t2 + 0.018203 * t3;
theta = (2004.3109 - 0.85330 * T - 0.000217 * T2) * t - (0.42665 + 0.000217 * T) * t2 - 0.041833 * t3;
zeta = ln_deg_to_rad (zeta);
eta = ln_deg_to_rad (eta);
theta = ln_deg_to_rad (theta);
/* calc A,B,C equ 20.4 */
A = cosl (mean_dec) * sinl (mean_ra + zeta);
B = cosl (theta) * cosl (mean_dec) * cosl (mean_ra + zeta) - sinl (theta) * sinl (mean_dec);
C = sinl (theta) * cosl (mean_dec) * cosl (mean_ra + zeta) + cosl (theta) * sinl (mean_dec);
ra = atan2l (A,B) + eta;
/* check for object near celestial pole */
if (mean_dec > (0.4 * M_PI) || mean_dec < (-0.4 * M_PI)) {
/* close to pole */
dec = acosl (sqrt(A * A + B * B));
if (mean_dec < 0.)
dec *= -1; /* 0 <= acos() <= PI */
} else {
/* not close to pole */
dec = asinl (C);
}
/* change to degrees */
position->ra = ln_range_degrees (ln_rad_to_deg (ra));
position->dec = ln_rad_to_deg (dec);
}
double ln_get_mean_sidereal_time (double JD)
{
long double sidereal;
long double T;
T = (JD - 2451545.0) / 36525.0;
/* calc mean angle */
sidereal = 280.46061837 + (360.98564736629 * (JD - 2451545.0)) + (0.000387933 * T * T) - (T * T * T / 38710000.0);
/* add a convenient multiple of 360 degrees */
sidereal = ln_range_degrees (sidereal);
/* change to hours */
sidereal *= 24.0 / 360.0;
return sidereal;
}
/*! \fn double ln_get_par_body_elong (double JD, struct ln_par_orbit * orbit);
* \param JD Julian day
* \param orbit Orbital parameters
* \return Elongation to the Sun.
*
* Calculate the bodies elongation to the Sun..
*/
double ln_get_par_body_elong (double JD, struct ln_par_orbit * orbit)
{
double r,R,d;
double t;
double elong;
/* time since perihelion */
t = JD - orbit->JD;
/* get radius vector */
r = ln_get_par_radius_vector (orbit->q, t);
/* get solar and Earth-Sun distances */
R = ln_get_earth_solar_dist (JD);
d = ln_get_par_body_solar_dist (JD, orbit);
elong = (R * R + d * d - r * r) / ( 2.0 * R * d );
return ln_range_degrees (ln_rad_to_deg (acos (elong)));
}
/*! \fn double ln_get_par_body_phase_angle (double JD, struct ln_par_orbit * orbit);
* \param JD Julian day
* \param orbit Orbital parameters
* \return Phase angle.
*
* Calculate the phase angle of the body. The angle Sun - body - Earth.
*/
double ln_get_par_body_phase_angle (double JD, struct ln_par_orbit * orbit)
{
double r,R,d;
double t;
double phase;
/* time since perihelion */
t = JD - orbit->JD;
/* get radius vector */
r = ln_get_par_radius_vector (orbit->q, t);
/* get solar and Earth-Sun distances */
R = ln_get_earth_solar_dist (JD);
d = ln_get_par_body_solar_dist (JD, orbit);
phase = (r * r + d * d - R * R) / ( 2.0 * r * d );
return ln_range_degrees (ln_rad_to_deg (acos (phase)));
}
/* Equ 20.3, 20.4 pg 126
*/
void ln_get_equ_prec (struct ln_equ_posn * mean_position, double JD, struct ln_equ_posn * position)
{
long double t, t2, t3, A, B, C, zeta, eta, theta, ra, dec, mean_ra, mean_dec;
/* change original ra and dec to radians */
mean_ra = ln_deg_to_rad (mean_position->ra);
mean_dec = ln_deg_to_rad (mean_position->dec);
/* calc t, zeta, eta and theta for J2000.0 Equ 20.3 */
t = (JD - JD2000) / 36525.0;
t *= 1.0 / 3600.0;
t2 = t * t;
t3 = t2 *t;
zeta = 2306.2181 * t + 0.30188 * t2 + 0.017998 * t3;
eta = 2306.2181 * t + 1.09468 * t2 + 0.041833 * t3;
theta = 2004.3109 * t - 0.42665 * t2 - 0.041833 * t3;
zeta = ln_deg_to_rad (zeta);
eta = ln_deg_to_rad (eta);
theta = ln_deg_to_rad (theta);
/* calc A,B,C equ 20.4 */
A = cosl (mean_dec) * sinl (mean_ra + zeta);
B = cosl (theta) * cosl (mean_dec) * cosl (mean_ra + zeta) - sinl (theta) * sinl (mean_dec);
C = sinl (theta) * cosl (mean_dec) * cosl (mean_ra + zeta) + cosl (theta) * sinl (mean_dec);
ra = atan2l (A,B) + eta;
/* check for object near celestial pole */
if (mean_dec > (0.4 * M_PI) || mean_dec < (-0.4 * M_PI)) {
/* close to pole */
dec = acosl (sqrt(A * A + B * B));
if (mean_dec < 0.)
dec *= -1; /* 0 <= acos() <= PI */
} else {
/* not close to pole */
dec = asinl (C);
}
/* change to degrees */
position->ra = ln_range_degrees (ln_rad_to_deg (ra));
position->dec = ln_rad_to_deg (dec);
}
/*! \fn double ln_get_heliocentric_time_diff (double JD, struct ln_equ_posn * object)
* \param JD Julian day
* \param object Pointer to object (RA, DEC) for which heliocentric correction will be caculated
*
* \return Heliocentric correction in fraction of day
*
* Calculate heliocentric corection for object at given coordinates and on given
* date.
*/
double ln_get_heliocentric_time_diff (double JD, struct ln_equ_posn *object)
{
double theta, ra, dec, c_dec, obliq;
struct ln_nutation nutation;
struct ln_helio_posn earth;
ln_get_nutation (JD, &nutation);
ln_get_earth_helio_coords (JD, &earth);
theta = ln_deg_to_rad (ln_range_degrees (earth.L + 180));
ra = ln_deg_to_rad (object->ra);
dec = ln_deg_to_rad (object->dec);
c_dec = cos (dec);
obliq = ln_deg_to_rad (nutation.ecliptic);
/* L.Binnendijk Properties of Double Stars, Philadelphia, University of Pennselvania Press, pp. 228-232, 1960 */
return -0.0057755 * earth.R * (
cos (theta) * cos (ra) * c_dec
+ sin (theta) * (sin (obliq) * sin (dec) + cos (obliq) * c_dec * sin (ra)));
}
/*! \fn double ln_get_ell_body_phase_angle (double JD, struct ln_ell_orbit * orbit);
* \param JD Julian day
* \param orbit Orbital parameters
* \return Phase angle.
*
* Calculate the phase angle of the body. The angle Sun - body - Earth.
*/
double ln_get_ell_body_phase_angle (double JD, struct ln_ell_orbit * orbit)
{
double r,R,d;
double E,M;
double phase;
/* get mean anomaly */
if (orbit->n == 0)
orbit->n = ln_get_ell_mean_motion (orbit->a);
M = ln_get_ell_mean_anomaly (orbit->n, JD - orbit->JD);
/* get eccentric anomaly */
E = ln_solve_kepler (orbit->e, M);
/* get radius vector */
r = ln_get_ell_radius_vector (orbit->a, orbit->e, E);
/* get solar and Earth distances */
R = ln_get_ell_body_earth_dist (JD, orbit);
d = ln_get_ell_body_solar_dist (JD, orbit);
phase = (r * r + d * d - R * R) / ( 2.0 * r * d );
return ln_range_degrees(acos (ln_deg_to_rad (phase)));
}
int ln_get_body_rst_horizon_offset (double JD, struct ln_lnlat_posn *observer,
void (*get_equ_body_coords) (double,struct ln_equ_posn *), double horizon,
struct ln_rst_time *rst, double ut_offset)
{
int jd;
double T, O, JD_UT, H0, H1;
double Hat, Har, Has, altr, alts;
double mt, mr, ms, mst, msr, mss, nt, nr, ns;
struct ln_equ_posn sol1, sol2, sol3, post, posr, poss;
double dmt, dmr, dms;
int ret, i;
/* dynamical time diff */
T = ln_get_dynamical_time_diff (JD);
if (isnan (ut_offset))
{
JD_UT = JD;
}
else
{
jd = (int)JD;
JD_UT = jd + ut_offset;
}
/* convert local sidereal time into degrees
for 0h of UT on day JD */
JD_UT = JD;
O = ln_get_apparent_sidereal_time (JD_UT);
O *= 15.0;
/* get body coords for JD_UT -1, JD_UT and JD_UT + 1 */
get_equ_body_coords (JD_UT - 1.0, &sol1);
get_equ_body_coords (JD_UT, &sol2);
get_equ_body_coords (JD_UT + 1.0, &sol3);
/* equ 15.1 */
H0 =
(sin (ln_deg_to_rad (horizon)) -
sin (ln_deg_to_rad (observer->lat)) * sin (ln_deg_to_rad (sol2.dec)));
H1 = (cos (ln_deg_to_rad (observer->lat)) * cos (ln_deg_to_rad (sol2.dec)));
H1 = H0 / H1;
ret = check_coords (observer, H1, horizon, &sol2);
if (ret)
return ret;
H0 = acos (H1);
H0 = ln_rad_to_deg (H0);
/* correct ra values for interpolation - put them to the same side of circle */
if ((sol1.ra - sol2.ra) > 180.0)
sol2.ra += 360;
if ((sol2.ra - sol3.ra) > 180.0)
sol3.ra += 360;
if ((sol3.ra - sol2.ra) > 180.0)
sol3.ra -= 360;
if ((sol2.ra - sol1.ra) > 180.0)
sol3.ra -= 360;
/* equ 15.2 */
mt = (sol2.ra - observer->lng - O) / 360.0;
mr = mt - H0 / 360.0;
ms = mt + H0 / 360.0;
for (i = 0; i < 3; i++)
{
/* put in correct range */
if (mt > 1.0)
mt--;
else if (mt < 0)
mt++;
if (mr > 1.0)
mr--;
else if (mr < 0)
mr++;
if (ms > 1.0)
ms--;
else if (ms < 0)
ms++;
/* find sidereal time at Greenwich, in degrees, for each m */
mst = O + 360.985647 * mt;
msr = O + 360.985647 * mr;
mss = O + 360.985647 * ms;
nt = mt + T / 86400.0;
nr = mr + T / 86400.0;
ns = ms + T / 86400.0;
/* interpolate ra and dec for each m, except for transit dec (dec2) */
posr.ra = ln_interpolate3 (nr, sol1.ra, sol2.ra, sol3.ra);
posr.dec = ln_interpolate3 (nr, sol1.dec, sol2.dec, sol3.dec);
post.ra = ln_interpolate3 (nt, sol1.ra, sol2.ra, sol3.ra);
poss.ra = ln_interpolate3 (ns, sol1.ra, sol2.ra, sol3.ra);
poss.dec = ln_interpolate3 (ns, sol1.dec, sol2.dec, sol3.dec);
/* find local hour angle */
Hat = mst + observer->lng - post.ra;
Har = msr + observer->lng - posr.ra;
Has = mss + observer->lng - poss.ra;
/* find altitude for rise and set */
altr = sin (ln_deg_to_rad (observer->lat)) * sin (ln_deg_to_rad (posr.dec)) +
cos (ln_deg_to_rad (observer->lat)) * cos (ln_deg_to_rad (posr.dec)) *
cos (ln_deg_to_rad (Har));
alts = sin (ln_deg_to_rad (observer->lat)) * sin (ln_deg_to_rad (poss.dec)) +
cos (ln_deg_to_rad (observer->lat)) * cos (ln_deg_to_rad (poss.dec)) *
cos (ln_deg_to_rad (Has));
/* must be in degrees */
altr = ln_rad_to_deg (altr);
alts = ln_rad_to_deg (alts);
/* corrections for m */
ln_range_degrees (Hat);
if (Hat > 180.0)
Hat -= 360;
dmt = -(Hat / 360.0);
dmr = (altr - horizon) / (360 * cos (ln_deg_to_rad (posr.dec)) * cos (ln_deg_to_rad (observer->lat)) * sin (ln_deg_to_rad (Har)));
dms = (alts - horizon) / (360 * cos (ln_deg_to_rad (poss.dec)) * cos (ln_deg_to_rad (observer->lat)) * sin (ln_deg_to_rad (Has)));
/* add corrections and change to JD */
mt += dmt;
mr += dmr;
ms += dms;
if (mt <= 1 && mt >= 0 && mr <= 1 && mr >= 0 && ms <= 1 && ms >= 0)
break;
}
rst->rise = JD_UT + mr;
rst->transit = JD_UT + mt;
rst->set = JD_UT + ms;
/* not circumpolar */
return 0;
}
void MainWindow::setSunRiseAndSetVectors(const QDateTime &dateTime)
{
struct ln_equ_posn equ;
struct ln_rst_time rst;
struct ln_zonedate rise, set, transit;
struct ln_lnlat_posn observer;
struct ln_hrz_posn hpos;
double JD;
observer.lat = ui->latEdit->text().toFloat();
observer.lng = ui->lngEdit->text().toFloat();
ln_date date;
date.years = dateTime.date().year();
date.months = dateTime.date().month();
date.days = dateTime.date().day();
date.hours = dateTime.time().hour();
date.minutes = dateTime.time().minute();
date.seconds = dateTime.time().second();
JD = ln_get_julian_day(&date);
/* ra, dec */
ln_get_solar_equ_coords (JD, &equ);
ln_get_hrz_from_equ(&equ, &observer, JD, &hpos);
double a = ln_range_degrees(hpos.az - 180);
QString s;
s.sprintf("Azimut: %0.3f", a);
ui->listWidget->addItem(s);
s.sprintf("Evaluation: %0.3f", hpos.alt);
ui->listWidget->addItem(s);
/* rise, set and transit */
if (ln_get_solar_rst (JD, &observer, &rst) == 1) {
ui->listWidget->addItem(QString("Zirkumpolar"));
} else {
ln_get_local_date (rst.rise, &rise);
ln_get_local_date (rst.transit, &transit);
ln_get_local_date (rst.set, &set);
s.sprintf("Aufgang: %02d:%02d:%02d", rise.hours, rise.minutes, (int)rise.seconds);
ui->listWidget->addItem(s);
s.sprintf("Transit: %02d:%02d:%02d", transit.hours, transit.minutes, (int)transit.seconds);
ui->listWidget->addItem(s);
s.sprintf("Untergang: %02d:%02d:%02d", set.hours, set.minutes, (int)set.seconds);
ui->listWidget->addItem(s);
}
//sunHeading->setVisible(false);
setSunVectors(&rise, &observer, sunRise);
setSunVectors(&set, &observer, sunSet);
mc->setView(QPointF(observer.lng, observer.lat));
//overlay->addGeometry();
}
int ln_get_object_rst_horizon_offset (double JD, struct ln_lnlat_posn * observer,
struct ln_equ_posn * object, long double horizon, struct ln_rst_time * rst, double ut_offset)
{
int jd;
long double O, JD_UT, H0, H1;
double Hat, Har, Has, altr, alts;
double mt, mr, ms, mst, msr, mss;
double dmt, dmr, dms;
int ret, i;
if (isnan (ut_offset))
{
JD_UT = JD;
}
else
{
/* convert local sidereal time into degrees
for 0h of UT on day JD */
jd = (int)JD;
JD_UT = jd + ut_offset;
}
O = ln_get_apparent_sidereal_time (JD_UT);
O *= 15.0;
/* equ 15.1 */
H0 = (sin (ln_deg_to_rad (horizon)) -
sin (ln_deg_to_rad (observer->lat)) * sin (ln_deg_to_rad (object->dec)));
H1 = (cos (ln_deg_to_rad (observer->lat)) * cos (ln_deg_to_rad (object->dec)));
H1 = H0 / H1;
ret = check_coords (observer, H1, horizon, object);
if (ret)
return ret;
H0 = acos (H1);
H0 = ln_rad_to_deg (H0);
/* equ 15.2 */
mt = (object->ra - observer->lng - O) / 360.0;
mr = mt - H0 / 360.0;
ms = mt + H0 / 360.0;
for (i = 0; i < 3; i++)
{
/* put in correct range */
if (mt > 1.0)
mt--;
else if (mt < 0)
mt++;
if (mr > 1.0)
mr--;
else if (mr < 0)
mr++;
if (ms > 1.0)
ms--;
else if (ms < 0)
ms++;
/* find sidereal time at Greenwich, in degrees, for each m */
mst = O + 360.985647 * mt;
msr = O + 360.985647 * mr;
mss = O + 360.985647 * ms;
/* find local hour angle */
Hat = mst + observer->lng - object->ra;
Har = msr + observer->lng - object->ra;
Has = mss + observer->lng - object->ra;
/* find altitude for rise and set */
altr = sin (ln_deg_to_rad (observer->lat)) * sin (ln_deg_to_rad (object->dec)) +
cos (ln_deg_to_rad (observer->lat)) * cos (ln_deg_to_rad (object->dec)) *
cos (ln_deg_to_rad (Har));
alts = sin (ln_deg_to_rad (observer->lat)) * sin (ln_deg_to_rad (object->dec)) +
cos (ln_deg_to_rad (observer->lat)) * cos (ln_deg_to_rad (object->dec)) *
cos (ln_deg_to_rad (Has));
/* must be in degrees */
altr = ln_rad_to_deg (altr);
alts = ln_rad_to_deg (alts);
/* corrections for m */
ln_range_degrees (Hat);
if (Hat > 180.0)
Hat -= 360;
dmt = -(Hat / 360.0);
dmr = (altr - horizon) / (360 * cos (ln_deg_to_rad (object->dec)) * cos (ln_deg_to_rad (observer->lat)) * sin (ln_deg_to_rad (Har)));
dms = (alts - horizon) / (360 * cos (ln_deg_to_rad (object->dec)) * cos (ln_deg_to_rad (observer->lat)) * sin (ln_deg_to_rad (Has)));
/* add corrections and change to JD */
mt += dmt;
mr += dmr;
ms += dms;
if (mt <= 1 && mt >= 0 && mr <= 1 && mr >= 0 && ms <= 1 && ms >= 0)
break;
}
rst->rise = JD_UT + mr;
rst->transit = JD_UT + mt;
rst->set = JD_UT + ms;
/* not circumpolar */
return 0;
}