Quadrant House Systems

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Chart of a Finnish politician, Placidus houses

These are a category of House Systems (also called unequal house systems,) because they normally give rise to houses encompassing varying numbers of degrees; although each house will have the same number of degrees as the house opposite to it (for example, the second and eighth houses). In contrast, a whole sign or Equal house system consistently yields houses of 30 degrees each.

Differences in Calculation

In a quadrant house system, the chart is divided into quarters by the Medium Coeli and Imum Coeli (midheaven or MC and IC) axis and by the Ascendant and Descendant axis. These lines form the cusps of the first, fourth, 7th, and 10th houses. In contrast, in an equal house or whole sign system, MC and IC will normally fall somewhere within their four houses. Examples of popular quadrant house systems are Placidus and Koch for birth charts, and the Regiomontanus system in horary astrology.

Same person, Equal houses[1]

Although all house systems in use today involve a projection of a 12-fold division of the cosmos onto the Ecliptic the various quadrant house systems differ in terms of several key concepts important in conceptualizing and dividing the three-dimensional space in which planets, stars, and abstract points move over the course of a day. House systems vary in terms of which reference points are used to bisect the Celestial Sphere and whether the house divisions represent measurements of segments of time or of distance.

For example, one could determine the “up-down” axis of a chart in terms of the highest point of the sun’s daily journey (the MC) and its opposite point (the IC) or as the highest point in the sky (the Zenith) and its opposite point, the Nadir. The ascendant/descendant axis might be calculated as the simple visible horizon positions of the sun at dawn and sunset, or as a projection of the earth’s equator outward onto the celestial sphere, the Celestial Equator. In visualizing the course of the sun from its point of dawn in the east to its highest point in its journey across the sky, one could measure the sun’s course in units of time (hours and minutes) or in units of distance, normally calculated as degrees.

Advantages and Disadvantages

Today astrologers disagree on which is the “best” house system to use. Proponents of quadrant house systems claim a level of accuracy in timing events which an equal house system, with cusps at 0 degrees or at the same degree of each sign, is unlikely to match.

On the other hand, unequal houses can contain very narrow houses and very wide ones, to the point where an entire sign may be intercepted within house cusps showing the adjacent signs.Some astrologers feel that an Intercepted Sign has no special significance, while others find them to have interpretive value. With very high latitude northern births, unequal houses may appear very skewed, indeed. With an equal house system where the angles appear embedded within houses, however, at high latitudes the MC and IC may also appear nowhere near their respective 1st, 7th, 10th, and 4th houses. With Scandinavian births, for example, it is possible for the MC to appear in the 12th house of a whole sign system.

Some astrologers recommend using different house systems for different individuals. For example, a man born with the sun right on the Cusp between two houses may identify more with one house than other, based upon his life experience. Some quadrant house systems will shift the sun into the house that makes the most sense to this individual. Also, the same astrologer may use a different house system for different types of astrology: for example, Placidus for natal chart interpretation and Regiomontanus for horary astrology.


Notes and References

  1. The MC appears in the 12th house