Astrological Signs and Houses

Nearly everyone knows that there are twelve astrological signs in the zodiac, and once a student has learned the basics, he or she learns that there are also twelve houses used by astrologers.

While nearly everyone seems to agree that each sign contains thirty degrees, and that in that sense the signs are equal in size, there is much disagreement about which method of house division to use.

There are some excellent resources describing methods of house division, and I have included some links at the end of this article.

Celestial Latitude seems to be largely neglected both in the signs and in the houses.  In the case of the signs, there appears to be a tacit assumption that the planets can be treated as though they had zero latitude, and in the Equal House System the same assumption is made, with six great circles running from the poles of the ecliptic and intersecting the ecliptic at right angles.

Many space systems of house division follow the same logic, using six great circles to divide the sky into twelve equal lunes.  Even the time-based Placidus System results in twelve houses of equal size, (in area on the celestial sphere), though they are by no means the same as each other in shape!  Celestial Latitude may be taken into account in these systems, though most software does not seem to do this automatically, at least when displaying a chart wheel.

Is there an alternative way of looking at signs and houses, using different assumptions?

Although the twelve signs may be equal along the ecliptic, there are an infinitude of possible systems where this does not hold away from the ecliptic.

We are so used to thinking in terms of latitude and longitude on earth, that it is easy to forget that there are other ways of mapping our own planet.  One such way is to consider mapping the earth by dividing it up into twenty equal area spherical triangles, giving a spherical icosahedron.

Now the celestial sphere can be divided up in an analogous way, into twenty equal spherical triangles.  It so happens that if the poles of the ecliptic are located in the precise centre of two of these spherical triangles, (obviously opposite one another), the great circle of the ecliptic passes through twelve of the other eighteen spherical triangles in such a way that all the twelve triangle boundaries occur at intervals of thirty degrees along the ecliptic.  We have equal signs along the ecliptic.

Celestial Latitude will have an effect on sign placement here.  Indeed, under some circumstances, if a planet or asteroid has a Celestial Latitude of more than plus or minus ten degrees it may not lie in any of the twelve recognised (triangular!) signs at all - maybe we need a few more sign names!

The same idea can be applied to the houses.  I particularly like the symmetry of an icosahedral house system with four of the vertices on the horizon, four on the meridian and four on the prime vertical.  There are twenty houses, which are quite easy to visualise on a clear night, once you get used to the idea.

Eight of these houses are completely above the horizon and eight completely below.  Four of the houses straddle the horizon, two near the north point and two near the south point.  Dwellers in high latitudes will probably acknowledge these "twilight zones" readily!

I am not suggesting in any way that traditional methods of sign division and house division should be abandoned.  However thinking about the platonic solids and their projections onto a sphere may bring additional insights into our work.  More anon!

Relevant links

Platonic Spheres

An Astrological House Formulary


Page created 24th February 2002

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