As we mentioned earlier, the astrological houses show us which spheres or aspects of life receive more weight than others in a horoscope. Each astrological house stands for a particular sphere. The house division of a horoscope varies from person to person, since it is calculated according to the exact time of birth and the geographic position of the place of birth. 

The horoscope is divided by two axes into the eastern and western hemispheres as well as into the day and night hemispheres. The four points of intersection of these two axes with the ecliptic determine the house division of the horoscope. This is usually based on a further division of each of the four quadrants by three. There are various mathematical models according to which the houses are calculated. Consequently there is quite a long list of differing house systems (Placidus, Regiomontanus, Equal, Vehlow, etc.). Most of these differ only in the method of calculation used to divide the quadrants. 

The transition from one house to another is not as clear as the change from one sign to another. Planets occupying a position near the end of a house are often interpreted as belonging to the next.
 
The Horizon
Ascendant and Descendant 
The individual and his complement 

This axis, which divides the horoscope into an 'upper' (day-side) and a 'lower' (night-side) half, represents the local horizon at the time of birth. That point at which the eastern horizon intersects the ecliptic is termed the ascendant. It is the beginning or cusp of the first house. In opposition to it, on the cusp of the seventh house, we find the descendant. We will discuss the interpretation of the houses on the following pages. Planets found near the ascendant at the moment of birth are rising, or have just risen, while planets close to the descendant are setting. 

The Meridian – A Vertical Division
Imum Coeli and Medium Coeli
Origins and orientation

The second important axis in house division is the meridian. This divides the horoscope into an eastern (on the left of the chart) and a western (on the right of the chart) half. The uppermost point of intersection of this axis with the ecliptic is called the Medium Coeli (MC) or midheaven, the lower point (situated under the horizon) is termed the Imum Coeli (IC). Planets close to the MC occupy the highest possible place in the heavens at the time of birth, while planets near the IC are so to speak under our feet on the other side of the earth.