Programming interface to the Swiss Ephemeris - programmiastral.com

Swiss Ephemeris 28
12. House cusp calculation
12.1 swe_houses()
/* house cusps, ascendant and MC */
int swe_houses(
double tjd_ut, /* Julian day number, UT */
double geolat, /* geographic latitude, in degrees */
double geolon,
/* geographic longitude, in degrees
* eastern longitude is positive,
* western longitude is negative,
* northern latitude is positive,
* southern latitude is negative */
int hsys, /* house method, one of the letters PKRCAV */
double *cusps, /* array for 13 doubles */
double *ascmc); /* array for 10 doubles */
12.2 swe_houses_armc()
int swe_houses_armc(
double armc, /* ARMC */
double geolat, /* geographic latitude, in degrees */
double eps, /* ecliptic obliquity, in degrees */
int hsys, /* house method, one of the letters PKRCAV */
double *cusps, /* array for 13 doubles */
double *ascmc); /* array for 10 doubles */
12.3 swe_houses_ex()
/* extended function; to compute tropical or sidereal positions */
int swe_houses_ex(
double tjd_ut, /* Julian day number, UT */
int32 iflag, /* 0 or SEFLG_SIDEREAL or SEFLG_RADIANS */
double geolat, /* geographic latitude, in degrees */
double geolon,
/* geographic longitude, in degrees
* eastern longitude is positive,
* western longitude is negative,
* northern latitude is positive,
* southern latitude is negative */
int hsys, /* house method, one of the letters PKRCAV */
double *cusps, /* array for 13 doubles */
double *ascmc); /* array for 10 doubles */
The function swe_houses() is most comfortable, if you need the houses for a given date and geographic
position. Sometimes, however, you will want to compute houses from an ARMC, e.g. with the composite
horoscope which has no date, only the composite ARMC of two natal ARMCs. In such cases, you can use the
function swe_houses_armc(). To compute the composite ecliptic obliquity eps, you will have to call
sweph_calc() with ipl = SE_ECL_NUT for both birth dates and calculate the average of both eps.
Note that tjd_ut must be Universal Time, whereas planets are computed from Ephemeris Time
tjd_et = tjd_ut + delta_t(tjd_ut).
Also note that the array cusps must provide space for 13 doubles, otherwise you risk a program crash.
The extended house function swe_houses_ex() does exactly the same calculations as swe_houses(). The
difference is that swe_houses_ex() has a parameter iflag, which can be set to SEFLG_SIDEREAL, if sidereal
house positions are wanted. Before calling swe_houses_ex() for sidereal house positions, the sidereal mode
can be set by the function swe_set_sid_mode(). If this is not done, the default sidereal mode, i.e. the
Fagan/Bradley, ayanamsha will be used.
There is no extended function for swe_houses_armc(). Therefore, if you want to compute such obscure things
as sidereal composite house cusps, the procedure will be more complicated:
/* sidereal composite house computation; with true epsilon, but without nutation in longitude */
swe_calc(tjd_et1, SE_ECL_NUT, 0, x1, serr);
swe_calc(tjd_et2, SE_ECL_NUT, 0, x2, serr);