Copyright for text and illustrations belongs to Ch. Weidner In
order to understand the origins of the different house systems
and the problems connected with them, it is helpful to discuss a
few terms of celestial mechanics which are important from an
astrological perspective for the construction of the respective
systems. The horizon system The horizon is the most important
reference level in astrology when it comes to the houses because
it forms the platform on which we experience ourselves as
observers of all phenomena. The horizon divides the celestial
sphere - at the centre of which the observer is located - into a
visible hemisphere above and an invisible hemisphere below. From
an astronomical point of view, the matter is not that simple:
astronomers differentiate between the The apparent horizon
exactly corresponds to the horizon which we perceive when we
talk about the 'horizon'. We could also say: the plane of the
apparent horizon is on the same level as the eyes of the
observer. The plane of the tru