Horoscopy is the art of casting horoscopes or divinations based upon the relative positions of heavenly bodies. It is often associated with horoscope, an important element in astrology which interprets the charcater and destiny of a person (or group of persons) according to the position of the planet, usually at the person's birth.
Derived from the Greek hora ('season') and skopia ('observation')
Along with the study of astrology, horoscopy developed in ancient Babylon and later spread to other nations like Greece and Rome.
Horoscopy is performed based on the information given by the person and it is then interpreted according to systematic principles. It considers the circle of the 12 signs of zodiac as they are crossed by the sun, moon and planets at differemt periods and the circle of 12 houses around which the circle of zodiac turns.
Casting a horoscope depends on acquiring the right data and time. 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.