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In astrology, a horoscope is a chart or diagram representing the positions of the Sun, Moon, planets, the astrological aspects, and sensitive angles at the time of an event, such as the moment of a person’s birth. The word horoscope is derived from Greek words meaning “a look at the hours” (horoskopos, pl. horoskopoi, or “marker(s) of the hour.”) Other commonly used names for the horoscope in English include astrological chart, astro-chart, celestial map, sky-map, star-chart, cosmogram, vitasphere, radical chart, radix, chart wheel, or simply chart. It is used as a method of divination regarding events relating to the point in time it represents and forms the basis of the horoscopic traditions of astrology.

In common usage, horoscope often refers to an astrologer’s interpretation, usually through a system of Sun sign astrology or based upon calendar significance of an event, as in Chinese astrology. In particular, many newspapers and magazines carry predictive columns based on celestial influences in relation to the zodiacal placement of the Sun on the day of a person’s birth, identifying the individual’s Sun sign or “star sign.” This system is distinct from horoscopes as traditionally employed, as only the zodiacal placement of the Sun is considered in interpretation. While this modern usage is perhaps the most popular in the colloquial lexicon, this article will focus primarily on the traditional concept.


The horoscope serves as a stylized map of the heavens over a specific location at a particular moment in time. In most applications the perspective is geocentric (heliocentric astrology being one exception). The positions of the actual planets (including Sun and Moon) are placed in the chart, along with those of purely calculated factors such as the lunar nodes, the house cusps including the midheaven and the ascendant, zodiac signs, fixed stars and the lots. Angular relationships between the planets themselves and other points, called aspects, are typically determined. Which elements are used or emphasized over others varies by tradition.


The word Latin horoscopus, ultimately from Greek ὡρόσκοπος “nativity, horoscope”, literally “observer of the hour [of birth]”, from ὥρα “time, hour” and σκόπος “observer, watcher”. In Middle English texts from the 11th century, the word appears in the Latin form, and is anglicized to horoscope in Early Modern English. The noun horoscopy for “casting of horoscopes” has been in use since the 17th century (OED). In Greek, ὡρόσκοπος in the sense of “ascendant” and ὡροσκοπία “observation of the ascendant” is in use since Ptolemy (Tetrabiblos 33, 75).

Concepts in Western Astrology

The native is the time and place of the event (a birth, for example) being charted, and is considered to be at the centre of the celestial sphere.
The celestial sphere is a sphere of arbitrary radius upon which the items appearing on the regard to their distance from the native.
The plane of the equator is the plane of the earth’s equator projected into space.
The plane of the ecliptic is defined by the orbits of the earth and the sun. For practical purposes the plane of the equator and the plane of the ecliptic maintain a constant inclination to each other of approximately 23.5°.
The plane of the horizon is centred on the native, and is tangential to the earth at that point. In a sphere whose radius is infinitely large, this plane may be treated as nearly equivalent to the parallel plane with its centre at the earth’s center. This greatly simplifies the geometry of the horoscope, but does not take into account that the native is in motion. Some writers on astrology have thus considered the effects of parallax, but most would agree that (apart from that of the moon) they are relatively minor
There are four primary angles in the horoscope (though the cusps of the houses are often included as important angles by some astrologers). The ascendant is the eastern point where the ecliptic and horizon intersect; the ascendant is generally considered the most important and personalized angle (along with the midheaven) in the horoscope by the vast majority of astrologers and the placement of its ruler, called the chart ruler is considered to be greatly important. Its opposite point in the west is the descendant. In creating a horoscope the ascendant is traditionally placed as the left-hand side point of the chart. During the course of a day, because of the Earth’s rotation, the entire circle of the ecliptic will pass through the ascendant and will be advanced by about 1°. This provides us with the term rising sign, which is the sign of the zodiac that was rising in the point on the ecliptic that is furthest above the plane of the horizon (not to be confused with zenith, which is normal to the horizon and so directly above the horoscope location). Its opposite point is known as the imum coeli (not to be confused with nadir, which is the opposite point of the zenith on the reverse side of the horizon). For events occurring where the planes of the ecliptic and the horizon coincide, the limiting position for these points is located 90° from the ascendant.

The zodiac

The astrological symbols/glyphs used in Western astrology to represent the astrological signs (Zodiac)

The zodiac refers to the 16° wide band on the celestial sphere containing the signs. It is centered on the ecliptic,occurs at the exact moment that the Sun crosses the celestial equator and enters the zodiac sign of Aries. Astrologers in India and some Western astrologers use the more ancient sidereal zodiac, which corresponds to the ancient position of the constellations as they were viewed thousands of years ago. Many people are confused regarding the difference between the sidereal constellations and the tropical zodiac signs. Because of a “wobble” in the earth’s axis of rotation over a period of about 26,000 years (this 26,000 year period is often called a “great year”), the point at which the vernal equinox advances in the sky rate is approximately 0 deg, 0 min, 50.23 seconds a year. Precession of the equinoxes thus occurs at a rate of roughly 5 arc minutes of a degree every 6 years. Sidereal and so the signs relate to the seasons and not the stars. It is also important to note that some astrologers don’t use the signs of the zodiac at all, focusing more instead on the astrological aspects and other features of the horoscope.
The sun sign is the sign of the zodiac in which the sun is located for the native. This is the single astrological fact familiar to most people. If an event occurs at sunrise the ascendant and sun sign will be the same; other rising signs can then be estimated at approximately two hour intervals from there.
A cusp is the boundary between two signs or houses. For some the cusp includes a small portion of the two signs or houses under consideration.


The houses are a series of twelve divisions of the plane of the ecliptic. Astrologers have devised many systems of calculating these house divisions. In the case of the equal house system the ecliptic is divided into twelve equal houses of 30° each. The first house begins at the ascendant and the others are numbered counterclockwise from that point. The first six are therefore below the horizon, and the other six are above. The positions of these houses remains fixed relative to the native. The signs and planets all move through the twelve houses during the course of a day, and the planets move through the signs over the course of months or years.

Construction of a horoscope in Western Astrology

To create a horoscope, an astrologer first has to ascertain the exact time and place of the subject’s birth, or the initiation of an event. The local standard time (adjusting for any daylight saving time or war time) is then converted into Greenwich Mean Time or Universal Time at that same instant. The astrologer then has to convert this into the local sidereal time at birth in order to be able to calculate the ascendant and midheaven. The astrologer will next consult a set of tables called an ephemeris, which lists the location of the sun, moon and planets for a particular year, date and sidereal time, with respect to the northern hemisphere vernal equinox or the fixed stars (depending on which astrological system is being used). The astrologer then adds or subtracts the difference between the longitude of Greenwich and the longitude of the place in question to determine the true local mean time (LMT) at the place of birth to show where planets would be visible above the horizon at the precise time and place in question. Planets hidden from view beneath the earth are also shown in the horoscope.
The horoscope 12 sectors around the circle of the ecliptic, starting from the eastern horizon with the ascendant or rising sign. These 12 sectors are called the houses and numerous systems for calculating these divisions exist. Tables of houses have been published since the 19th Century to make this otherwise demanding task easier..


Okie. Information overload.

The next one would be something much lighter and comprehensive.