A History and Comparative of House Systems
by Tishelle Betterman

The earlier astrologers and astronomers provided us a wide mixture of house systems from which to choose today. Each one contains its own history and a different way to view the age-old question of how to calculate intermediate house cusps. A great majority of our house systems originated thousands of years ago, many as an attempt to clarify Ptolemy’s ambiguous rendition of how to calculate houses in Tetrabiblos. Equal, Porphyry, and Regiomontanus are explained below, each revealing surprising and interesting histories as well as fascinating variations in chart interpretation.

Although the Babylonians did not use house systems, they did provide the basis to accurately calculate the Ascendant and Midheaven. (1) According to North in Mathematical Principles and Their History, the Babylonians “gave the rising times of the signs of the zodiac, . . .on the basis of observation, but [only] as [they] fit conveniently into an arithmetical progression with . . . the ratio 3:2, their ratio for [the] longest to shortest daylight.” (2) Like the Babylonians, the Greeks did not place importance on the use of houses either. (3) In the closing years of the century Before Christ (BC) and the first 600 years AD, Greek horoscopes rarely identified a specific point or degree. In reviewing horoscopes of Neugebauer and van Hoesen, North found only 27 of the 168 reviewed, indicated an Ascendant or Midheaven, 2 of the168 included house division, and 2 out of 51 noted a “calculated degree for [the] Midheaven.” (4)

Despite the general disinterest during the Hellenistic Period to use houses or calculate cardinal angles, the last half of second century BC saw the emergence of mathematically-minded astrologers “inserting the astronomical Midheaven degree in horoscopes.” (5) By the start of the third century, the idea was born that the 10th house cusp be calculated and notated. (6) As described below, it was not until later when the Islamic and Christian astrologers began delineating horoscopes that we saw importance given to the cardinal angles (Ascendant, Imum Coeli, Descendant, and Midheaven). (7)

Equal House System
One of the primary astrological writers of the second century was Claudius Ptolemy (100-178). Many regard him as the principle astronomer and astrologer of the Classical World (8), and thus, his astrological book, the Tetrabiblos, has often been considered the ultimate resource in astrology, even in the Modern era. (9) In A History of Horoscopic Astrology, Holden states that in fact, Ptolemy’s astrological work outlined in Tetrabiblos was apparently a revised version of basic Greek astrology. (10)

The house system ascribed to Ptolemy through his writings is the Equal house system. In this method of calculating the house cusps, the degree and minutes of longitude for the Ascendant (the point where the ecliptic intersects the horizon on the eastern side of the meridian) or Midheaven (the point at which the ecliptic and meridian intersect on the south side of the prime vertical) is the starting point. All the remaining cusps are measured in 30-degree increments from that point. Thus, each house cusp contains the same degree and minute of longitude as the Ascendant or Midheaven, but progresses through the astrological zodiac one sign at a time around the chart wheel. The Equal house system therefore is not “latitude-dependent” and the 4th and 10th house cusps are not on the meridian. (11) In other words, if the Ascendant is used as the starting point, the Midheaven is not the 10th house cusp, and if the Midheaven is used as the starting point, the Ascendant is not the 1st house cusp. 

Porphyry House System
The Porphyry house system is attributed to the Greek philosopher and Neoplatonist, Porphyry (233-305 AD). It may be possible that Porphyry derived this system from an unknown astrologer, Orion (around 150 – 175 AD). (12) Porphyry re-introduced the house system in his book, Introduction to Ptolemy’s Tetrabiblos, written in c. 295 making it one of the earliest quadrant house systems. (13)

A quadrant house system divides the celestial sphere into four sections between the horizon and meridian great circles. (14) The horizon is a great circle which cuts through the center of earth and extends infinitely into space, and upon which an observer or event is placed. The meridian is another great circle that passes through the zenith (the point directly overhead a location or observer and perpendicular to the horizon), as well as the north and south points of the horizon. Where the meridian crosses the plane of the horizon, this point of intersection is called the North Point. The quadrants are then further divided into three segments, thereby creating twelve houses.

This period in history saw the emergence of ecliptic-based house systems, in which the ecliptic is utilized to identify the cusps of the astrological houses. Ecliptic is defined as “the earth’s orbit [or great circle] which, from a geocentric position, is seen as the sun’s path” around the celestial sphere, and is inclined 23° 27’ to the earth’s equator.” This inclination is known as the obliquity of the ecliptic. (15) The ecliptic system is based on the “earth’s orbital plane” around the sun and the earth’s tilt on that plane. The equinoxes or points where the ecliptic and equator intersect provide the first point of reference for longitude measurement. (16)

In the Porphyry house system, both a quadrant and ecliptic-based system, the arc, or distance along the ecliptic, between the true longitude of the Midheaven and the Ascendant is measured providing the diurnal semi- arc (the part of the ecliptic above the horizon and in the eastern quadrant). (17) This semi-arc is then trisected into three equal arcs. The eleventh and twelfth house cusps become the points where these trisections intersect the ecliptic. The arc between the true longitude of the Ascendant and Imum Coeli (the point on the ecliptic north of the prime vertical where the meridian intersects) are then found and trisected as well to determine the cusps of the second and third houses. The remaining house cusps are calculated at 180° the opposite cusp (where the 8th house cusp is opposite the 2nd). (18)

Regiomontanus House System
Regiomontanus is one of most commonly used house system by horary astrologers. (19) This method is named after Johann Müller (1436-1476), an educated native of southern Germany, more commonly known by his Latin name Regiomontanus. (20) However, the origin of the Regiomontanus house system does not begin with Müller; instead, evidence suggests the likelihood that this method originated with the Arabs (21) probably around the eleventh century AD. (22) 

In Horoscopes and History, North indicates the existence of some debate as to the origins of Regiomontanus. However, his research, based on available documents, appears to result in the conclusion that the Arabs are responsible for the formulation of Regiomontanus or as North calls it, the Equatorial (fixed boundary). Below, North states his reasoning behind this conclusion:

". . .it seems quite certain that al-Jayyini, had the method of casting the houses later ascribed to al-Ghafuqi and now known universally as Regiomontanus’s method. It is possible that al- Jayyini, a notable mathematician, developed the mathematics needed for drawing up tables for that method. . .And. . ., it is not improbable that Regiomontanus knew of his work on the subject. (38) . . .certainly we have no earlier name than al- Jayyini to tag on to the Equatorial (fixed boundary) procedure." (23)

"…the myth of their [Campanus and Regiomontanus] invention. . .has been so persistent [it] is surprising, in view of the fact that these two fixed boundary methods are described in several of the so-called ‘Alfonsine’ books, collected together under the patronage of Alfonso X (‘el sabio’) of León and Castile in the thirteenth century. . . . (24) [And in these] references. . .[therein lies] the evidence. . . for the use of the Equatorial (fixed boundaries) system before Regiomontanus. . ." (25)

Astronomical tables were critical to the practice of astrology in the 11th and 12th centuries. As Western Europe became bored with the adventures of the Crusaders and the drudgery of farm life, the people looked to foreign places to seek knowledge. One of the results was an increase in the number of scholars, which then required a larger quantity of astronomical (or astrological) tables. The Arabs became a prime source for these tables. (26) One of the first sets available was from astronomer al-Zarqali (1029-1100). He arranged the Toledan Tables for use specifically by the Europeans. (27) Eventually al-Zarqali’s tables were replaced by the Alfonsine Tables, a collection of astronomical tables created under the sponsorship of Spanish Alphonso X (1226-1284). Both of these tables played an important part in Western astrology. Like the Toledan Tables, the Alfonsine Tables were available for two to three hundred years. (28)

The popularity of Regiomontanus was most likely the result of two factors. First, the house cusps are fixed for an observer at a particular latitude, and can thus be “inscribed on an astrolabe plate,” making it possible to calculate the houses quickly. (29) Secondly, with the help of Marin Bylica in 1467, Müller developed a comprehensive set of tables, called the Tabulai directionum profectionumquem, for the Regiomontanus house system. Between the astrolabe and set of tables, the Regiomontanus method grew in popularity across all of Europe during the sixteenth century, eventually replacing the favored Alcabituius method. (30)

In Regiomontanus, beginning at the East Point, or the intersection of the Prime Vertical and horizon on the east side of the Meridian, the celestial equator (otherwise known as the earth’s equator projected into the celestial sphere) is divided into equal, 30-degree arcs using house circles (great circles that pass through the north and south points of the horizon). Where the house circles intersect the ecliptic, the longitudes of the house cusps are measured, providing the degree and minute of the cusps. (31) Because the celestial equator is not perpendicular to the house circles, the houses are not equal. (32)

Comparative
So what differences result from these three distinct ways of calculating a chart? There are several significant variations that appear when you compare the Equal, Porphyry, and Regiomontanus house systems. Not only do the size of houses change, but planets and cusp rulers also shift between houses.

Example 1 displays an Equal house chart with Taurus rising. In this case, the Ascendant is the starting point upon which the rest of the house cusps are measured in 30-degree increments. By nature, Equal house systems cannot have intercepted houses because each house cusp must use the subsequent zodiac sign as it progresses around the chart wheel. We can see by comparing Example 1 with the Porphyry (Example 2) and Regiomontanus (Example 3) methods, that both Example 2 and Example 3 contain intercepted houses.

As such, it is easy to surmise that there are differences in the cusp rulers as well. Example 1 displays the 4th and 5th house rulers as Leo and Virgo respectively. The Porphyry house system, or Example 2, indicates the 4th house is ruled instead by Cancer, with Leo intercepted in the same house. Example 3, or Regiomontanus, is different still from both the Equal and Porphyry methods with Leo ruling the 5th house, Virgo intercepted in the 5th, and the 6th house ruler as Libra. Thus, it is evident that there can be significant differences between methods of calculating intermediate house cusps. The variations in cusp rulers in the lower and upper hemispheres can make a significant difference in the interpretation of a chart. When cusp sign changes so does the planet ruling the house and thereby the experiences associated with it.

Another significant shift is the placement of planets. In our three examples, there are obvious differences between the 4th and 7th houses. In the Equal house system, the Sun, Uranus, Mars, and Pluto are all located in the 5th house, placing a tremendous amount of energy in creative endeavors and children. Venus sits practically stage center in the 4th house while the Moon is just 5 degrees into the 7th house. The Porphyry method shows us a mild shift in planetary placement. The Sun and Uranus move a few degrees back into the 6th house and the Moon shifts into the 8th. Additionally, Saturn works its way from the 1st house into the 2nd and Venus now sits on the 5th house cusp. Many astrologers may still interpret these planets as if they were positioned in the same houses as the Equal method since the movement backwards is fairly minimal and generally within 5 degrees of the next house cusp. However, combined with the different house cusp rulers, the Porphyry method could easily be interpreted quite differently.

The most significant change occurs between the Equal system and the Regiomontanus system, especially concerning the changes in planetary placement between the 5th and 
6th houses. The Sun and Uranus are clearly 6th house planets in Regiomontanus instead of 5th house concerns as identified in the Equal system. The Moon and Saturn are in the same houses, but Chiron has now shifted from the 11th house in Example 1 to the 12th house in Example 3.

A quick glance between all four examples will reveal two more interesting points. First, each system displays variations of house sizes. The Equal house system quite obviously contains equal proportion between its houses, yet comparatively Porphyry and Regiomontanus have a combination of wide and thin houses. It is also interesting to note that a shift takes place regarding which houses are large and small in the Porphyry and Regiomontanus configurations as the Ascendant changes. Example 2 has a rising sign of Taurus and we can see the 10th, 11th, and 12th houses (and their opposites) are very large. However, if we look at Example 4 with an Ascendant of Sagittarius, a difference of more than half the zodiac away, this distortion of small and large houses shifts so that the 10th through the 12th are quite small. 

Secondly, and very worth considering, are the cardinal angles. In all three methods, the Ascendant - Descendant axis contain the same degree, minute, and sign. This is due to the fact that the Ascendant is used as a definable point in all house systems. Thus, every house system (with the exception of Whole Signs, which only uses signs not degrees) will bear the same Ascendant. However, if the Equal house system used the Midheaven as its definable point, the true Ascendant would not be the first house cusp. A further review reveals that only Porphyry and Regiomontanus methods share the same 10th house cusp, which is also the true Midheaven. Both of these house systems also utilize the Midheaven as another definable point in determining the intermediate cusps. The Equal system, however, uses only one - the Ascendant or Midheaven.

Each of the three house systems - Equal, Porphyry, and Regiomontanus - were a product of the people, tools, and reality of life in the period in which they were created. We have the Equal house system that only required either an Ascendant or Midheaven calculation to determine the approximate placement of the planets. Soon to follow was Porphyry, developed at a time when a little more emphasis was being placed on the importance of cusps. Its calculations were still quite simple and could be done quickly in the head once the Midheaven and Ascendant are found. And finally, Regiomontanus reflected the popularity of using tables and astrolabes during the 11th and 12th centuries to calculate house cusps. By understanding the history and astronomical functions of each method, we can fully understand the benefits and shortcomings of the numerous house systems available to us.

EXAMPLE 2

EXAMPLE 3

***********************
Endnotes:
(1) Lee Lehman. “Houses” (Kepler College: Symposium Lecture, 2001)
(2) J.D. North. Horoscopes and History (Gateshead: Paradigm Print, 1986), 7.
(3) Ibid., 7.
(4) Ibid., 6.
(5) James Holden, A History of Horoscopic Astrology (Tempe: American Federation of Astrologers, Inc., 1996), 91
(6) Ibid., 91.
(7) J.D. North. Horoscopes and History (Gateshead: Paradigm Print, 1986), 7.
(8) James Holden, A History of Horoscopic Astrology (Tempe: American Federation of Astrologers, Inc., 1996), 42.
(9) Ibid., 43.
(10) Ibid., 44.
(11) J.D. North. The Mathematical Principles and Their History (Gateshead: Paradigm Print, 1986), 42.
(12) James Holden, A History of Horoscopic Astrology (Tempe: American Federation of Astrologers, Inc., 1996), 50.
(13) Ibid., 62.
(14) Bob Makransky, Primary Directions (Occidental: Dear Brutus Press, 1988),17.
(15) Bruce Scofield. Astrological Chart Calculations, An Outline of Conventions and Methodology (Kepler College, Course 201 documentation, 2001), 2.
(16) Ibid., 3.
(17) Ibid., 9.
(18) Michael P. Munkasey. An Astrological House Formulary. National Council for Geocosmic Research, Inc. 4 Sept. 2001. <http://www.geocosmic.org/HouseArticle.html>, 6. 
(19) North. Horoscopes and History (Gateshead: Paradigm Print, 1986), 21.
(20) James Holden, A History of Horoscopic Astrology (Tempe: American Federation of Astrologers, Inc., 1996), 149.
(21) Arabs refer to those in general who speak and write in the Arabic language.
(22) In the 8th century, the Arabs began to obtain some of the remaining books from classical Greek period, including some on astrology and astronomy, which they translated into Arabic. (Holden, 99)
(23) J.D. North. The Mathematical Principles and Their History (Gateshead: Paradigm Print, 1986), 44.
(24) Ibid., 33.
(25) Ibid., 35.
(26) James Holden, A History of Horoscopic Astrology (Tempe: American Federation of Astrologers, Inc., 1996), 130.
(27) Ibid., 139.
(28) Ibid., 130.
(29) J.D. North. Horoscopes and History (Gateshead: Paradigm Print, 1986), 27-27.
(30) Ibid., 28.
(31) Bob Makransky, Primary Directions (Occidental: Dear Brutus Press, 1988), 35.
(32) Kevin Burk. Astrology, Understanding the Birth Chart (St. Paul: Llewellyn Publications, 2001), 169.



Bibilography
Burk, Kevin. Astrology, Understanding the Birth Chart (St. Paul: Llewellyn Publications, 2001)

Holden, James Herschel. A History of Horoscopic Astrology (Tempe: American Federation of Astrologers, Inc., 1996)

Lehman, Lee. “Houses” (Kepler College: Symposium Lecture, 2001)

Makransky, Bob. Primary Directions (Occidental: Dear Brutus Press, 1988)

Munkasey, Michael P. An Astrological House Formulary. National Council for Geocosmic Research, Inc. 4 Sept. 2001. <http://www.geocosmic.org/HouseArticle.html>

North, J.D. Horoscopes and History (Gateshead: Paradigm Print, 1986)

- - -, The Mathematical Principles and Their History (Gateshead: Paradigm Print, 1986)

Scofield, Bruce. Astrological Chart Calculations, An Outline of Conventions and Methodology (Kepler College, Course 201 documentation, 2001)

© Tishelle Betterman 2002

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