Ascendant

The Ascendant, called in Greek the horoskopos, the hour-marker, is the degree of the ecliptic rising over the eastern horizon at a given moment and place. It is not a body at all but a calculated point, and it is the single most important element in the classical system: the whole word horoscope comes from its Greek name, and the division of the chart into twelve houses is reckoned from it. Because the Earth turns once in twenty-four hours, the Ascendant moves through the entire zodiac in a day, about one degree every four minutes, which is why an accurate birth time matters and why astrology is sensitive to place as well as to time. The Ascendant governs the first house and is taken as the significator of the body, the appearance, the constitution and the native as an embodied person, and its ruling planet is the chart ruler.

Hellenistic technique gave the Ascendant a further role beyond signifying the body: it is the fixed reference point from which every one of the Hermetic lots, Fortune, Spirit and the rest, catalogued in this atlas among the Arabic parts, is projected, so that an error in the Ascendant's calculated degree propagates into every lot derived from it as well as into the house cusps themselves, making an accurate birth time the single most consequential piece of data a chart depends on.

The ascendant is the degree of the ecliptic crossing the eastern horizon, and computing it needs three things: the moment, the geographic longitude, which fixes the sidereal time, and the geographic latitude. That last dependence is what separates it from the Midheaven, which needs only the first two.

It completes a full circuit in one sidereal day, 23 hours 56 minutes and 4 seconds, so it averages one degree every 3 minutes and 59 seconds. The average is misleading. The ecliptic is inclined to the equator, so the rate is strongly uneven and the unevenness grows with latitude. At the latitude of northern Europe the signs from Capricorn to Gemini can rise in well under an hour each while those from Cancer to Sagittarius take three hours or more, an effect the classical writers knew as the signs of short and long ascension. Two people born an hour apart in the same city can therefore share a rising sign or be two signs apart, depending only on which part of the zodiac was on the horizon.

Two boundary cases are worth knowing. At the geographic poles the horizon coincides with the celestial equator, the ecliptic cuts it at two fixed points, and the ascendant does not move at all. Beyond the polar circles the rate becomes extreme enough that quadrant house systems built on the time a degree takes to rise, chiefly Placidus and Koch, stop being defined.

The Ascendant orients an entire chart to one specific time and place, which is why two people born on the same day, even in the same city, can have noticeably different horoscopes once the hour is taken into account. Because the eastern horizon carries the whole ecliptic past it roughly once every twenty four hours, the Ascendant shifts by about one degree every four minutes, making it one of the most time sensitive points a chart uses. It served as a foundational device of Hellenistic horoscopy from at least the second century CE, when it is recorded under its Greek name, horoskopos, in the works of Vettius Valens and Claudius Ptolemy; Ptolemy's Tetrabiblos even devotes a chapter to the influence of the four angles the Ascendant heads.

In Latin astrological writing, such as the Mathesis of Firmicus Maternus, the same point appears among the cardines, the Latin term for the angles that survives in modern usage as the "cardinal" points of a chart. In current notation the Ascendant is abbreviated AC or Asc, and it is conventionally drawn at the nine o'clock position on the now standard circular wheel chart, a diagramming convention that itself replaced older square format horoscopes, used across Western, Indian and Chinese astrology for centuries, only around the nineteenth century.