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Tables of Houses. Tables showing the degrees of the Signs which occupy the cusps of the
several Houses in different latitudes for every degree of Right Ascension, or for every 4 minutes
of Sidereal Time. Generally available are those by Dalton (1913), Raphael (1920) and Hugh
Rice (1935).

There is much argument anent the various systems of calculating the cusps of the intermediate
Houses, until one wonders sometimes why not use a stop watch to locate the degree on the
horizon every two hours. Of course it would have to be done over again in all latitudes, and
besides it would not be very scientific. Nevertheless the general opinion is that none of the
existing methods are correct for all latitudes, even though they may be near enough for practical
purposes. The four best known systems are as follows:

Campanus. The vertical circle from the zenith to the cast and west points of the horizon is
trisected. Through these points are drawn great circles, the House circles, from the north and
south points of the horizon. Thus the intersections will be at altitudes of 30° and 60° above the
horizon, on both cast and west branches of the prime vertical. This divides the sky into six great
sectors. Similarly divide the hemisphere below the horizon. The house cusps are the points at
which the ecliptic at that moment intersects the horizon.

Regiomontanus. The celestial circle is trisected, instead of the prime vertical, and great circles
extend from north and south points of the horizon to the points of trisection. The house cusps are
at the points at which the ecliptic intersects the horizon. At the Equator the two systems give the
same cusps, the disparity increasing as one approaches the Earth's poles.

Horizontal. Starting with great circles at the meridian and ante-meridian, the horizon and the
prime vertical, add other great circles from Zenith to Nadir which trisect each quadrant of the
horizon. The cusps will then be the points at which on a given moment the ecliptic intersects the
vertical circles.

Placidus Instead of using great circles, the diurnal motion of the Earth causes a celestial object
to intersect the cusp of the 12th House, after a sidereal-time interval equal to one-third of its
semi-diurnal arc; to intersect the cusp of the 11th House after a sidereal-time interval equal to
two-thirds of its semi-diurnal arc; and to culminate at the meridian after an interval of sidereal
time that corresponds to the semi-diurnal arc. The semi-arc from the meridian that intersects the
Eastern horizon gives the Ascendant; and the 2nd and 3rd house cusps are similarly extended
below the horizon. The Placidian cusps are in almost universal use at the present time. Maurice
Wemyss takes exception to the Placidus cusps on the grounds that the Ascendant is located
according to one system and the intermediate cusps by another. He prefers what he terms the
"Rational Method" of Regiomontanus.