The Horizon in an Astrological Chart is more commonly called the Ascendant.
It can only be determined through the precise time of birth.
(4 minutes = 1 degree)

The Rising Sign refers to the whole sign (30 degrees)
in which the Ascendant can be found on a single degree.
It determines personality, physical appearance
and influences the way that individuals are perceived by others.

In addition to the time of Birth,
both the longitude and latitude of the Birth place
(city, town or village)
are used to calculate the Ascendant.
Once the Ascendant is established,
the division of the 12 sectors or Houses is calculated.

For example, the House (or sector)
in which the Sun is found at your birth
is of great importance.
It is the heart of your Astrological Chart.

Of course, these Houses (or sectors) are not divided equally.
Depending on the season, the Sun does not always rise
or set at the same time.

A serious Astrological study takes these small discrepancies
into account when drawing up a Chart.

However, the Sun is always at its zenith at midday,
no matter what time it rises.
Called the "Midheaven", this culminating degree
corresponds to the axis of the 10th House.

Note that each House has certain similarities
which correspond to the 12 Signs of the Zodiac.

House 1 \ Aries
House 2 \ Taurus
House 3 \ Gemini
House 4 \ Cancer
etc...

Although all are important,
here are the more significant Astrological Houses.

House 1 = Ascendant (AS)
House 4 = Nadir (IC)
House 7 = Descendant (DS)
House 10 = Midheaven (MC)

These correspond to the Horizon and Meridian,
which are the principal axis of an Astrological Chart.