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. However, no studies have shown any scientific support for the accuracy of horoscopes, and the methods used to make interpretations are, at best, pseudo-scientific.

In common usage, horoscope often refers to an astrologer‘s interpretation, usually through a system of Sun sign astrology or based on 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” based on a conventional zodiac (which is not the celestial one). Such a concept is distinct from horoscopes as typically employed, where only the traditional 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.

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

Angles

  • 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 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 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. Here is an example: a person born on, say August 28, 2002 would come to understand that his/her Sun sign was Virgo according to western astrology (conventional Sun sign dates August 23, to September 22, of every year), but Sun on that same calendar date of the year 2002 was in the constellation Leo (where it had been since August 10, 2002 and would remain until September 15, when it would then finally cross into Virgo).

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.

Houses

  • 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.