How Astrological House Cusps Are Formed

Have you ever wondered how planetary forces in outer space can have distinctive influences upon a person’s life?  How exactly are they compartmentalized to correspond to specific areas of one’s life in real time and space?

To answer this question, one must understand the nature of astrological houses and how they are formed.  A key component to keep in mind is TIME in the context of three areas: the ecliptic plane, the earth’s equator (north or south latitude), and the local horizon.

Of the three components in time, it is the last one with respect to the local horizon that is critically the most important to calculating house cusps.  Due to the earth’s daily rotation, the plane of the local horizon is constantly changing in relation to the ecliptic.  What this means is that while aspects (i.e., mathematical angular relationships) between the planets tend to be constant throughout a specific day (with the exception of the Moon), the house cusps will vary considerably from one location to the next

Therefore, being able to pinpoint the exact latitude and longitude of birth is paramount.  This is especially true when a particular planet(s) is predominate in one’s life and activities—as would be the case when a planet is conjunct, opposition, parallel or contraparallel the all-important major angles of the Ascendant (ASC), Descendant (DSC), Medium Coeil (MC) or Imum Coeli (IC).  Furthermore, the exactness and accuracy of house cusps become even more important when it comes to accurate forecasting and identifying important milestones in life. No significant event happens in life without involvement of the Sun, Moon, ASC/DSC or MC/IC angles.

1. The first component regarding time relates to the ecliptic plane.  It is the elliptical path in which the earth and other planets orbit, or revolve, around the Sun.  Time in context of the ecliptic plane corresponds to the earth’s 365-day rotation around the Sun as well as the 360° Tropical Zodiac signs it enters and passes through along the way—with 0° Aries (Vernal Equinox) being around March 20-March 21:

2. The second component regarding time relates to the Earth’s equator.  It connects the North and South poles and is titled on its axis about 23.5 degrees from the plane of the ecliptic.  It not only refers to earth’s daily 24-hour rotation but also the seasons we experience, known as spring, summer, autumn, and winter.  Since earth is tilted on its axis, all portions of the earth do not experience the seasons at the same time.  For example, when it’s summer in the Northern hemisphere (north latitude), it’s winter in the Southern hemisphere (south latitude) and vice versa.  Lastly, it measures planetary aspects in declination (those that are parallel north or south of the equator), as opposed to longitude (what can be observed in a horoscope).  

3. The last component regarding time, and the one most important for calculating house cusps, relates to the local horizon (or local space), which identifies the specific time zone and precise birth location of an individual. 

After identifying the Ascendant and Midheaven, the diurnal arc is determined and then divided into six equal segments in longitude. The diurnal arc is the bow-shaped path of the Sun traversing the East-West dividing line on the ecliptic during daylight hours and corresponds to the upper six houses (12, 11, 10, 9, 8, and 7). 

These segment divisions in longitude correspond with fixed, unequal times in reference to noon, when the Sun is at its apex in relation to the birth locale. The direct counterpart of the diurnal arc in longitude is the nocturnal arc—180° apart (and 12 hours in time) when the Sun is below the horizon, or at its lowest point.

Having established the diurnal arc from the Sun’s position at noon—and the Sun being at the center of the ecliptic—these segment divisions (or six dividing lines) are then translated, or projected, unto the ecliptic to form what we visually see as house cusps, or an astrological chart/horoscope.