HOUSE SYSTEMS
Placidus
Placidus divides diurnal and nocturnal semi-arcs by time; its intermediate cusps depend on latitude and the recorded birth instant.
The idea in context
A time-based quadrant system that divides the diurnal and nocturnal motion used to define intermediate house cusps. The Ascendant and Midheaven anchor the 1st and 10th cusps.
MAKE IT CONCRETE
An example to picture
At one latitude the 2nd House may span fewer zodiac degrees than the 3rd House. This unequal width is expected, not missing chart data.
How to read it
Inspect the actual computed cusps and Ascendant, and verify the local birth time before reading a planet close to a boundary.
A common misunderstanding
Placidus is not defined at every polar latitude. A calculator should report unsupported geometry instead of silently substituting Equal House.
BRING IT BACK TO YOUR LIFE
A question to sit with
Which near-cusp placement would you want to check against the birth record before interpreting it?
Go deeper: the full reference
How to read it
Its houses are often unequal in zodiacal width. Read a placement in the house actually calculated, rather than assuming one sign corresponds to one house.
Input and calculation limits
Placidus may be undefined at high latitudes. Synastry reports an unsupported calculation instead of silently substituting a different system.
Compare one choice at a time
Changing the house system changes cusps and may change house assignments. It does not move the planets through the zodiac. These are interpretive frameworks, not measured personality traits or predictions. Private chart settings do not change dating compatibility.
Try reading your own birth chart
Create a free birth chart, select the placement or symbol you are learning about, and read it alongside this lesson. A planet’s sign, house and aspects add context; keep your recorded birth time and chart settings in view.
Connect the ideas
Whole Sign
The entire zodiac sign containing the Ascendant is the 1st House. Each following sign forms the next house, with cusps at sign boundaries.
2 min readEqual House
The exact Ascendant degree begins the 1st House, followed by eleven equal 30° sectors along the zodiac.
2 min readKoch
A time-based quadrant system using the birthplace latitude and the diurnal arc associated with the Midheaven to construct intermediate cusps.
2 min readPorphyry
Each zodiacal arc between successive primary angles is divided into three equal portions to form the intermediate house cusps.
1 min read