The Horary Astrology is a branch of ancient or vedic astrology and is practiced by the astrologer to answer a question by constructing Horoscope chart at the time when the question was raised. The astrologers generally use this technique when he doesn’t have the accurate date, time and place of birth of the concerned person.
To know more about Horary astrology, follow this link: http://en.wikipedia.org/wiki/Horary_astrology