Horary astrology
Horary astrology answers a specific question from a chart cast for the moment the astrologer understood it, rather than from anyone's birth chart.
The technique is the most rule-bound branch of the art. The querent is signified by the ruler of the Ascendant, the thing asked about by the ruler of the house that governs it, and the answer turns on whether those two significators perfect an aspect before either changes sign.
Because the judgement is mechanical, horary is where the classical conditions matter most: reception, besiegement, a planet under the beams, and the void-of-course Moon, which Lilly treats as a sign that nothing will come of the matter.
Frequently asked
Do I need a birth chart for a horary question?
No. The chart is cast for the moment and place the question was understood, which is what makes horary usable when no birth data exists.
What makes a horary chart unreadable?
The classical strictures: an Ascendant in the very first or last degrees, or a void-of-course Moon, both read as the question not being ripe.