Rising sign calculator

Your rising sign, or ascendant, is the sign that was coming up over the eastern horizon at the minute and place you were born. It is the starting point of the whole chart: it fixes where the twelve houses begin, and it is read as the way you meet the world, the first impression you give and the manner people notice before they know you well.

The Earth turns once a day, so every sign rises in turn, and the rising sign changes on average every two hours. The pace is uneven. At the latitude of New York, Aries and Pisces each take about 70 minutes to rise while Virgo and Libra take about two and a half hours; at London the quickest sign rises in under an hour and the slowest in almost three. South of the equator the pattern is reversed. A birth time that is out by twenty minutes can therefore give the wrong rising sign, and a date alone cannot give one at all.

With a time, the calculator also looks either side of it. If the sign on the horizon changed within ten minutes of the time you gave, the result says so, because times on records are often rounded to the nearest five or fifteen minutes.

Without a time, StarMap steps through your birth date every two minutes at your birthplace and lists each sign with the stretch of local clock time it was rising. There are usually thirteen rows, because the sign rising at midnight comes round again before the day ends. If you know you were born in the morning, or after lunch, or late at night, the table usually cuts twelve possibilities down to two or three. On a day the clocks changed, the table says so and marks the hour that happened twice.

Your time may be easier to find than you think. In the United States the long-form birth certificate usually shows it. In England and Wales it is recorded only for twins and other multiple births, while Scottish certificates include it. Hospital notes and baby books often have it, and a parent's memory of the hour is worth trying: enter it, then see whether the result warns that a change was close.

The ascendant is the point where the eastern horizon meets the ecliptic, the Sun's yearly path through the zodiac. StarMap finds it from the sidereal time at your birthplace and the tilt of the Earth's axis on your birth date, then places it in the tropical zodiac. Checked against the Swiss Ephemeris, StarMap's angles agree to within a hundredth of an arcminute.

Then read the description under your result, and find the planet that rules your rising sign in your whole chart; astrologers call it the chart ruler. Many people also read the horoscope for their rising sign as well as their Sun sign, because the rising sign decides which house each part of the sky falls in.