Ascendant
The ascendant of a given geographic location at a given point in time is the point on the zodiac which coincides with — i.e., is ascending over — the eastern horizon as viewed from that place and time.
Briefly, the Ascendant is the precise degree (01 of 360) of the zodiac rising over the eastern horizon of the birthplace at the moment of birth. There are exactly 30 degrees per astrological sign, and because 12 multiplied by 30 equals 360 which is the span of the ecliptic, all twelve signs rise and fall during the course of one 24-hour day. This exact rising degree forms the first house cusp of a horoscope and is said to be of great personal significance in the character and life of the individual. The planet that rules the astrological sign rising in the East at the moment of birth is said to be the chart ruler.
Because all twelve of the zodiac signs rise and set during one 24-hour day and about one degree of the ecliptic rises about every four minutes, each sign takes approximately two hours to rise and set depending on the time of year; thus, because it takes the earth about 24 hours to do a full 360 degree turn on its axis, all twelve signs rise and set each day.
An exact birth time is vital to calculating the Ascendant with accuracy. When looking at the natal chart, the Ascendant is located on the cusp of the First House of your astrological chart — or at the nine o'clock position.
Since this is (usually) the cusp of the 1st house in a standard natal chart many modern astrologers believe that it naturally correspond to Aries, the 1st astrological sign in the Natural Zodiac.
But these assumptions were not always made. For one thing, ancient astrologers used whole-sign house systems almost exclusively, which meant that each house of the chart began at 0 degrees of each sign. The first house was the one in which the point of the Ascendant fell; but the Ascendant itself did not form the boundary of the house. Secondly, the concept of each house having a corresponence to a zodiacal sign, which is sometimes called natural houses or the natural zodiac is a modern one. In the original formulations of astrology, Mars, which rules Aries, the first sign, actually was most at home and most powerful in the sixth house, not the first. Mercury was actually most effective in the first house, or Ascendant; and Mercury is the ruler of Virgo and Gemini.
The Ascendant is of great significance in all schools of astrology due to the fact that it serves as the filter through which everything in a natal chart- including the Sun and Moon- is expressed. Thus, most astrologers believe that the Rising Sign exerts an influence equal to or more powerful than that of the Sun and Moon signs. In Jyotish (Hindu astrology), the Ascendant is without question the most individual and defining element in the chart, and a modern-day Indian, when asked for his or her sign, will usually reply with the sign of their Ascendant
