THE RISING SIGN, OR ASCENDANT
The rising sign, or Ascendant, is the zodiac sign that was climbing the eastern horizon at the hour and place you were born. It is the cusp of your First House, and the point from which all your other houses are raised. Where your Sun sign answers “what,” the rising sign answers “how you arrive”: the face you lead with.
It changes every two hours
Across a day the whole zodiac appears to wheel past the horizon. The signs are not moving around us; the Earth is turning, a full three hundred and sixty degrees every twenty-four hours. Divide that by twelve and a new sign climbs the eastern horizon roughly every two hours. This is why the rising sign needs your birth time, not just your birth date.
The orbit and the spin
Two motions happen at once. The Earth orbits the Sun, one full revolution a year. The Earth also rotates on its own axis, one full turn a day.
Your planet signs, your Sun in Scorpio, your Mercury in Aquarius, come from the slow yearly orbit: they say which stretch of the zodiac each planet stood in front of. Your rising sign comes from the fast daily spin: it says which stretch was on your eastern horizon at that exact minute. The first changes over weeks. The second changes every couple of hours.
Two births, opposite sides
Imagine two people born at the very same instant, but on opposite sides of the Earth. Their planet signs are nearly identical: from either place, the planets sit in front of the same far constellations.
What changes is their horizon, literally what each of them sees to the east. Standing on opposite faces of a turning globe, they look out at different parts of the zodiac. Same charts, different risings. It is the one piece of the chart that is truly local to you.
Find your rising sign.
Because it turns on the minute and the place, you need your birth time and city. Enter them and the Ascendant, and the twelve houses raised from it, will be computed for the exact moment you arrived.