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.
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 traditions.
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, drifting by one day from the Greogrian Calendar every 72 years. 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).