Ecliptic-based houses

Let’s look at each of the major house systems one by one with a view to understanding how they are calculated and how this might affect the symbolism of the horoscope.

The easiest house systems to calculate are the ones that are directly based on the ecliptic. The three major house systems based directly on the ecliptic are (1) the whole sign house system, (2) the equal house system, and the (3) Porphyry house system.

To understand these systems and what they might symbolise, let’s review what the definition of the celestial circle known as the ecliptic.   

The ecliptic is the plane of Earth’s orbit around the Sun. From the perspective of an observer on Earth, the Sun’s movement around the celestial sphere over the course of a year traces out a path along the ecliptic against the background of stars.

Here is a helpful illustration of the ecliptic:

As you can see from the illustration, the Earth revolves around the Sun and as it does so, from the perspective of someone on Earth, we see the 12 signs of the zodiac, a different sign each month! The ecliptic in the above diagram is the celestial circle in red, which, being a circle, is divided into 360° of celestial longitude, and is the circle we see represented in two dimensions when we look at a horoscope.

In astrology, each of these signs which we find along the ecliptic are divided up into 30° of celestial longitude. Of course, astronomically speaking, these constellations of stars do not literally and uniformly take up exactly 30° of longitude, indeed some of them are larger and some are smaller. It was towards the end of the 5th century B.C. that Babylonian astrologers divided the ecliptic into 12 equal “signs”, by analogy to the 12 months, each sign containing 30° of celestial longitude, thus creating the first known celestial coordinate system.

This system of division of the ecliptic was used by the ancient Greeks in the form that is now called “whole sign houses”, where the division of the ecliptic was made into 12 portions of 30° each, each of these portions known as “houses”.  The two other house systems that were used during this period were the equal house system, and the Porphyry method of division.

It is not my purpose here to debate the prevalence of one house system over another during the Hellenistic period, nor will I make any attempt to conjecture how and for what purpose these systems were used in ancient times. My aim here is to simply define how these systems are calculated and how we might begin thinking of their symbolic significations in a contemporary context.

The Whole Sign House System:

  • The Whole Sign House system uses the zodiac signs on the ecliptic to define the twelve houses.
  • The zodiac sign which rises over the horizon at the time of the birth or event defines the entire first house. The remaining eleven signs create the rest of the houses, moving in a counter-clockwise direction.
  • Each house begins at 0° of the zodiac sign and ends at 29° and is thus 30° in size.
  • This is a non-quadrant house system and does not use the ascendant or midheaven to define the beginning of the first and tenth houses. The ascendant and midheaven in this system are floating. The ascendant always defines the first house. The MC can be present anywhere between the ninth and eleventh houses.

The Equal House System:

  • The Equal-House system is a variation of the Whole sign House system (WSH). The difference is that the degree of the ascendant defines the start of the first house and becomes the starting degree of each of the remaining eleven houses.  The MC floats and does not define the start of the tenth house.
  • Symbolically speaking, the personal point of the degree of the ascendant is emphasized in this system as a defining feature which dictates the remaining eleven house cups. The symbolism becomes a bit more tied to the earth in that the eastern horizon takes on an elevated importance.
  • The equal house system is a non-quadrant house system.

Porphyry – a quadrant house system:

In quadrant house systems the ascendant and descendant define the first and seventh house cusps, and additionally, the midheaven (MC) is used to define the tenth house cusp, while its opposite point the I.C. (Imum Coeli) defines the cusp of the fourth house.

This creates four sectors or zones within the circle of the ecliptic, otherwise known as quadrants.

The earliest quadrant house system, used in Hellenistic times, is known as the Porphyry house system, named after the third century Neo-Platonist Porphyry, although he was not its creator as this system was described in the second century by Vettius Valens in his astrological textbook entitled Anthology.

In the Porphyry system of houses, the span of the ecliptic between the horizon and midheaven is trisected equally to produce three houses. Because the number of degrees between the horizon/ascendant and MC/midheaven varies according to location, time of day and season, the quadrants are not of equal size.

So, the three houses from the rising quadrant, i.e., from the degree to the culminating degree (MC), houses 12, 11 and 10, will be a different size to the setting quadrant, i.e., houses 9, 8 and 7.

This difference is carried over diagonally across the horoscope into the houses below the horizon.

So, in Porphyry, the ascendant forms the first house cusp, and the MC forms the 10th house cusp.  The Porphyry system, though quadrant, is still based on the ecliptic, as are whole sign houses and equal-houses. Yet one could say that symbolically it is more earth based in that a heightened important is given to the ascendant and MC; also, the geographical location of where the chart is cast is highlighted insofar as the cusp of the first and tenth houses reflect the earth-bound location.

Initial conclusions: Whole Sign houses, Equal-houses and Porphyry houses are arrived at through division of the ecliptic, which is a celestial circle. So in order to understand its symbolism, we need to reflect upon what the various celestial circles might symbolise.

The celestial circles used to arrive at the major house systems are as follows:

  • The ecliptic
  • The prime meridian (runs north through south through the poles)
  • The prime vertical (runs east through west through the zenith)
  • The celestial equator (which is projected from the earth’s equator)

Returning to our consideration of the ecliptic, where is the ecliptic located? 

It is the apparent path the Sun takes around the earth when viewed from an earth-based, geocentric perspective.

It is extra-lunar rather than sublunar.

A good deal of symbolism could be drawn from this.  We will begin to consider it after we have covered the other major house systems and how they are calculated.

Next up: House systems coming out of the astrolabe.