Astrological house systems provide the means through which astrologers can account for the physical environment in which we live. Essentially to accomplish this end, the zodiac is divided into twelve (12) pieces called houses. Each house deals with a specific aspect of life such as our body, our parents, our job, our children, our friends and so forth. Astrologers since the turn of the current era, (approx. 1st century ce) have used some form of house system.
In current times, there are three classes of house systems that exist: ecliptic based, time based, and space based, which in total yield around twenty different ways (or house systems) to divide the 360 degree zodiac mathematically. When you are looking at one chart and change the house system, the planets appear to shift into different houses, even though the planets don’t change their zodiacal position.
Which house system to use is a highly debatable topic among astrologers. Today, the three most popular house systems used in tropical astrology are Equal house, Placidus, and Koch. In Indian and Hellenistic astrology, the whole sign house system is used alongside a secondary house system, such as the Equal or Porphyry house system.
Equal House System
The equal house system calculates the degree of the Ascendant, which is uses as the beginning or cusp of the first house. Let’s say the Ascending degree is determined to be 27 degrees of Gemini. Each subsequent house cusp begins at 27 degrees of the next sign. So the second house would begin at 27 degrees of Cancer, the third house would begin at 27 degrees of Leo, and so forth through the 12th house cusp. Equal houses essentially means that each house contains 30 degrees – no more and no less. Some astrologers do not like this system because it does not equate the 10th house cusp with the Midheaven (which indicates the degree that is highest in the sky above the horizon at the place of birth). However, the Midheaven can certaintly still be noted in this house system as well as any planet forming an aspect to that angle. The Equal house system is also very good to use the closer you get to the poles, or the higher latitudes. In these locales other house systems become very distorted.Placidus House System
The Placidus system is a time based system and was actually invented by an Italian monk, named Placidus de Titis who lived in the first half of the 17th century. However, it was not readily used until after an English astrologer, John Partridge, worked with it heavily and popularized it in the 18th century. Because of his work, affordable tables were made available in the 19th century that permitted astrologers to do the necessary mathematical calculations required to use the system. It is important to remember that astrologers did not have computers until the mid to late 80s and thus all these calculations were done by hand. Astrologers were limited to the ephemeris and tables available to them, which usually contained the information they needed to calculate a certain house system at their present and nearby latitudes. So Placidus became the most prominent house system in the western world in modern times because of the availability of its data tables and the work done by John Partridge. It is popular because its system is based on dividing the time it takes the Ascendant to become the Midheaven, which means metaphorically that this house system reflects how a person grows and develops throughout life.This house system, along with Koch (popularized in the 1970’s by a German astrologer Walter Koch), starts by calculating the Ascendant, followed by the Midheaven. In these systems, the Midheaven actually becomes the cusp (start) of the tenth house. The other house cusps are calculated using different algebraic calculations. It is possible in both these house systems that some zodiac signs may never appear on a house cusp at all, so you may have a Gemini ascendant, and the beginning of the second house may be Leo, skipping Cancer all together.
Koch House System
In the Koch house system the Midheaven is considered the most important point in the chart along with the geographical environment in which a person is born. Here, the Midheaven is linked with the ego as well as to who one is and what they wish to become. So this system emphasizes individual freedom and free will and therefore is very popular among amoung astro-psychologists and spiritualists. So when astrologers are working with someone who has been fortunate enough to have the freedom to become who they want, this system would appear to be one of the the more suitable choices.Whole House System
Whole houses are calculated very simply. Once the Ascending degree has been identified, the first house contains all 30 degrees of the same sign as the Ascendant. For example, if the Ascendant was 24 degrees of Aries, the first house would contain all points and planets in the sign of Aries. You could say that the first house begins at 0 degrees Aries. The second house would contain all 30 degrees of Taurus and the third house would contain 0 - 30 degrees of Gemini. This pattern sequentially through the zodiac until all 12 signs have been 'assigned' a house. This system continues to be used in Jyotish and Hellenistic astrological traditions.Porphyry House System
The Porphyry house system was named after the Neo-Platonist and Greek philosopher, Porphyryr (c. 233-304), however, he was likely not the inventor of the calculations since this method of calculating houses was made by Vettius Valens (150 - 175 CE) in Book III, Chapter 2 of his Anthology. Valens attributes the method to an unknown astrologer named Orion. This house system continues to be used in Hellenistic and Jyotish astrology.Essentially Porphyry is an ecliptic based system that derives the non-angular house cusps by trisecting the arc between the Ascendant and Midheaven. Thus, once the Ascendant and Midheaven ecliptic positions are calculated the arc is computed by subtracting one from the other and dividing the remainder by 3 to identify the arc of each intermediate house. This was a fairly easy calculation to be done. The Porphyry house system retains both the Ascendant and Midheaven as the cusps of the 1st and 10th house respectively.
Written by: © 2006 Tishelle Betterman, "Astrolady"