Placidus is the default choice and is the most commonly used house system among astrologers. It is a safe choice. If however, you want to understand more about the house system you are using, read the comparison between different systems. Think about the methods and reasoning behind each system and compare the differences in the chart drawings that result from them. Then read our intuitive introduction to house systems, which invites you to look at the sky itself.
'Configure Chart Drawing' is the place to set the house system for the current chart. To set a new default house system for all charts, go to the Preferences menu.
House systems can be selected in the 'Configure Chart Drawing' page of Clairvision Virtual Astrologer. To set and save a particular choice, go to 'Preferences'.
Placidus is the system which is most often used by astrologers. That does not necessarily mean that it is the best (astrologers, apart from rare exceptions, do not have much understanding of the mathematical realities behind the figures they handle daily). Placidus is certainly a system that makes sense, and it is devoid of some aberrations found in some other systems. But it should always be kept in mind that if it is omnipresent, it could be more due to habit than to its intrinsic value.
The Placidus system is based on time. The cusps (limits between houses) are determined so that it takes the same time for a planet to move through each house above the Ascendant (on the day side of the chart). And each house below the Ascendant (on the night side) is crossed within a fixed duration too, but this time is not equal to that needed to move through the houses above the Ascendant.
The Placidus system, in relation to its time-based definition, fitted well with primary directions, a prediction tool based on relatively heavy mathematical calculations. Astrologers, however, have long given up primary directions, but they have retained Placidus!
A major weakness of Placidus is that it does not work for high latitudes. Past 66° (North or South), it becomes completely meaningless; the formulae can no longer be applied. Campanus does not have this limitation. (Try to enter a chart with 70 degrees of latitude North or South while Placidus is selected as the default house system, and see what happens.)
In contrast to the Placidus division of houses, which is based on time, the Campanus one is based on space.
Campanus determines house cusps by dividing the prime vertical into equal parts (the prime vertical is the great circle of the celestial sphere which passes right on top of your head, and through the western and eastern horizons of the place where you are located).
Without going into maths, it must be said that the logic which is behind Campanus makes a lot of sense. If astrologers were to choose their house system by understanding the formulae rather than repeating what they have been told to do, it is quite likely that Campanus would be the world standard.
Another major advantage of Campanus is that it can be used for any point on the surface of the Earth, unlike Placidus whose formulae stop working for high latitudes.
However, it must be noted that, in practice, Placidus and Campanus give quite similar results. When switching from one system to the other, most planets will remain in the same house. Thank God!
Based on an irregular division of time, the Regiomontanus house system has lost most of the popularity it enjoyed at the time of the Renaissance.
Regiomontanus is a minor system, which was included in Clairvision Virtual Astrologer more for curiosity than for any practical applications.
Originated by Walter Koch in the nineteen-sixties, the Koch house system is probably the modern system which has gained the most momentum – not rising enough to rival Placidus in any way, but certainly gaining more acceptance than other new systems.
The principle is similar to Placidus (trisection of semiarcs), and the limitations are similar – it can't be applied to high latitude areas.
The mathematical principles behind it are far from being magnificent, and only the future will tell if Koch is one of many fads or if it will stay. However, as discussed before, these things often have more to do with personal influence and marketing skills than with the soundness of the formulae involved.
Based on the ecliptic, the Equal House system is the most rudimentary of all house systems. Starting from the Ascendant, the Equal House system places the house cusps every 30 degrees, dividing the chart wheel into twelve segments of equal longitudes.
Note that in the Equal Houses system the Ascendant and the cusp of the 10th house are always exactly 90 degrees apart – that's the very definition of the system: every house must be exactly 30 degrees wide.
With this in mind, it's clear that the Midheaven and the cusp of the tenth house cannot be identical: there is more to the Midheaven than just being the cusp of the tenth house. The Midheaven is an astronomical point (ie the intersection of the local meridian with the ecliptic), and that point is of course not always 90 degrees away from the Ascendant.
The major drawback with this system is that apart from two moments of the day (when the sidereal time = 6h and 18h) the cusp of the 10th house does not coincide with the Midheaven. This makes this house system difficult to support.
Of no real practical use, this system was included in Clairvision Virtual Astrologer mainly for curiosity.
The Bihorary house system uses a system of coordinated on the celestial equator. Its 12 houses are equal, but in right ascension, not in longitude (which the Equal Houses system uses). With Bihorary houses, the meridian is the reference.
A minor house system which was introduced some time in the 20th century but never really gained momentum.
(There are 2 fundamental systems of coordinates on the celestial sphere:one based on the ecliptic (longitude and latitude); and one based on the celestial equator (right ascension and declination).
The Porphyry house system is possibly the oldest and most simple system. It is named after a student of Plotinus, in the 2nd century, but its use is thought to predate its namesake. The Porphyry house system is based on the ecliptic. It calculates the Ascendant and Midheaven and from these it then calculates the other house cusps. The zodiacal longitudes between the Ascendant and Imum Coeli are divided into three equal angles, as are those in the sector between the Medium Coeli and the Ascendant.
In Porphyry Houses, the houses 4, 5, 6, 10, 11 and 12 are equal. Houses 1,2,3,7,8 and 9 are also equal, but the two groups are not necessarily equal to each other.
Published by the Arabic astrologer Alcabitius in the 10th century, this house system originated at least as early at the 5th century. It became known to Western astrologers in the 12th century when it was translated into Latin and was popular among astrologers of the late middle ages and early Renaissance periods. The Alcabitius house system is a time-based, equatorial equivalent of the Porphyry system, with calculations done according to right ascension. However the system is known to become unworkable at extreme latitudes close to the poles.
On the celestial equator, houses 1,2,3,7,8 and 9 are equal. Houses 10,11,12,4,5 and 6 are also equal but not to the former.
Because extravagant claims were made about this system, and because a number of astrologers have believed these claims without any form of critical appreciation, it is necessary to say at least a few words about it.
The 'topocentric' house system was elaborated in Argentina in the nineteen-sixties by Nelson Page and Vendel Polish. The formulae behind it are nothing more than a simplified version of Placidus. The authors claimed that their system, unlike Placidus, made it possible to establish house cusps for polar regions, but the mathematical substantiation they presented was 'very vague', to be polite.
They moreover claimed that their system allowed them to make predictions to the second, on bases which are both mathematically and philosophically unacceptable.
One can only be sad when seeing astrologers become really enthusiastic about such systems on the basis of faith, without any understanding of the formulae behind them, and without any substantiation of the claims of predictions.
Abenragel houses were formulated by Haly Abenragel, court astrologer to the Tunisian prince in the first part of the 11th century. The house system is based on a unique system of circles that define the boundaries of the houses.
The Abenragel system is used by some European astrologers, under the name of APC (Ascendant Parallel Circle).
copyright © 2008 Samuel Sagan, Ruth Helen Camden.