Horary astrology is an ancient branch of horoscopic astrology by which an astrologer attempts to answer a question by constructing a horoscope for the exact time and place at which the question was asked. The answer might be a simple yes or no, but is generally more complex with insights into, for example, the motives of the questioner, the motives of others involved in the matter, and the options available to him.
Horary astrology has been practiced for centuries in India known as Prasna Shastra (Sanskrit prasna = question). It is a branch of Vedic astrology which is still widely used across the Indian subcontinent. The more advanced form is the Astamangalam Prasna and Deva Prasna methods of Kerala. The state of Kerala, in India, is famous even today for its traditional use of horary astrology.
The English astrologer William Lilly (1602-81) was the last major horary astrologer, and probably the best-known horary practitioner in history. His book Christian Astrology is in print and widely used in the modern day practice of horary astrology. Today, horary astrology is still used much more in the United Kingdom, with medium popularity remaining in America, Germany, France, and the other Western European nations. Influential modern practitioners of horary astrology following Lilly's technique include UK astrologers Olivia Barclay, founder of the Qualifying Horary Practitioner (QHP), Barbara Dunn, Principal of QHP John Frawley, (runs courses), Deborah Houlding, Principal of STA, Susan Ward, Principal of a horary diploma course, and American astrologers J. Lee Lehman, (runs courses), and Christopher Warnock (runs courses).
Horary astrology has its own strict system. The position of and aspects to the moon are of prime importance. The person asking the question, or querent, is represented by the ruler of the sign the first house cusp falls on in the horoscope. Planetary aspects to the house cusps are considered more important than in other branches of astrology (although it is the planetary rulers of the houses in question that take precedent in analysis). Other key elements used in horary astrology include the luna nodes, the planetary antiscia, and the Arabic parts.
Typically, a horary chart is read by first assigning the thing asked about, the quesited, to a particular house in the chart. For instance, asking "Where is my lost dog?" would be represented by the sixth house, as it is the house that governs small animals (traditionally, smaller than a goat). The house cusp of the sixth house will be in a particular sign, for example Libra. Libra is ruled by Venus, so Venus is considered the significator of the lost dog. Venus's state in the horoscope (its dignity, aspects, etc.) will give clues to the animal's location.
Fundamental to horary astrology is the concept of planetary dignity and reception. Dignity comes in two forms, essential and accidental. Essential refers to the quality of a planet at a particular degree of the zodiac and its ability to express its true/good nature. For instance, a horoscope is drawn and Mars is in Scorpio. Using traditional rulerships, Mars here is in its own sign, so it is considered essentially strong; a well-behaved Mars. Mars in Taurus, on the other hand, is in its detriment, so is essentially weak. In a horary question where Mars is a significator, Mars's essential dignity will indicate something of the quality of the quesited. Accidental dignity refers to how the planet "finds itself". That is, if the [[planet is in a traditionally bad house (6th, 8th, or 12th) in the chart, if it is retrograde]], aspected by a malefic planet (Saturn or Mars), combust, etc, then it is considered an accidental debility.
As a metaphor, consider an actor who breaks his leg on opening night; essential good, accidentally debilitated. The converse is true. A planet in poor essential dignity may have considerable accidental power. Taking the earlier example of Mars, if Mars was in Scorpio, and in an angular house in the horary chart (1st, 7th, 10th, 4th) then it is considered accidentally as well as essentially strong. It has quality, and power to act, to express.
Reception refers to how each planet in a horary question chart "view" or "receive'" each other, either favourably, unfavourably, or somewhere in between. If Mars is in Taurus, and Venus is in Scorpio, then each of the planets is in the sign the other planet rules. (Venus is ruler of Taurus, Mars of Scorpio). This is called mutual reception by rulership, and although each planet is in its detriment, it nevertheless receives the other planet favourably. In some horary questions, a thorough understanding of receptions (and the above example skims the surface of this topic) is required to delineate the interplay of how the various significators view each other what sort of attitudes are taking place in the area of the question.