Placidean

The house system devised by the Spanish monk, Placidus de Tito (seventeenth century). Placidus’ system, still widely used today, is based on the trisection of nocturnal and diurnal semi-arcs. The time it takes for each degree of the ecliptic to rise from the lower meridian to the horizon (nocturnal semi-arc) and to rise from the horizon to the upper meridian (diurnal semi-arc) is adapted to space.