Houses · Intermediate
Placidus houses
Also called Placidus
A time-based house system: each cusp is where a degree has travelled a set fraction of its daily arc.
Named after the seventeenth-century monk Placidus de Titis, it became standard in English-language astrology because printed tables for it were widely available. It is undefined near and inside the polar circles, where some degrees of the zodiac never rise or never set. This site then says so and offers Whole Sign or Equal instead, never switching silently.
- How it is worked out
- The eleventh and twelfth cusps sit at one and two thirds of their diurnal semi-arc from the Midheaven; the second and third at two and one thirds of their nocturnal semi-arc from the Ascendant; solved by iteration.
Sources
- Astrodienst AstroWiki: Placidus (opens in a new tab) practitioner
- Swiss Ephemeris documentation (Astrodienst): house systems, nodes and calculation conventions (opens in a new tab) technical
Written for Cool Moon Facts in its own words. An astrology source documents what astrologers believe or practise; it does not establish that astrology works.