A map of the sky at your birth
A natal chart, also called a birth chart, is a diagram of where the Sun, Moon and planets stood in the sky at the exact time and place you were born. It is drawn as a circle divided into twelve slices called houses. Around the rim sit the twelve zodiac signs, and the planets are placed on the circle at the positions they held in the sky at that moment.
Astrologers treat the chart as a portrait of temperament and tendency, not a verdict. Two people born on the same day can have very different charts, because the Moon travels about thirteen degrees in a day and the rising sign changes roughly every two hours. This is why a Sun sign alone, the kind of horoscope printed in a newspaper, covers only a small part of the picture.
What you need to build one
Three facts are required: the date, the time and the place of birth.
The place matters because the sky looks different from different spots on Earth. It gives the latitude and longitude that fix the horizon and the angles of the chart. The time matters most for the rising sign and the houses. A difference of four minutes in birth time moves the rising degree by about one degree, so a time rounded to the nearest hour can change the whole house layout. A birth certificate or hospital record is the best source for the time.
If the time is unknown, a chart can still show the planets in their signs, but the houses and the rising sign cannot be trusted. Some astrologers use a noon chart in that case and leave the houses out.
What is inside the chart
Planets. The Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto each stand for a drive or function. The Sun is core identity and vitality. The Moon is emotional need and habit. Mercury is thinking and speech. Venus is attraction and values. Mars is drive and anger. Jupiter is growth and optimism. Saturn is structure and limits. Uranus, Neptune and Pluto move slowly and shape whole generations, so their signs are shared by millions of people.
Signs. Each planet sits in one of the twelve signs, and the sign describes the style in which the planet works. Mars in Aries acts fast and openly. Mars in Taurus acts slowly and stubbornly. The drive is the same and the manner is different.
Houses. The twelve houses describe areas of life: self, money, communication, home, romance, daily work, partnership, shared resources, learning and travel, career, friends and rest. The planet shows what, the sign shows how and the house shows where it plays out. See the page on the 12 houses.
Aspects. Aspects are the angles between planets, such as the conjunction, square, trine and opposition. They show how different parts of a chart cooperate or clash. See the major aspects.
Angles. Four sensitive points mark the frame of the chart: the Ascendant on the eastern horizon, the Descendant opposite it, the Midheaven at the top and the Imum Coeli at the bottom.
The big three
Start with the Sun, the Moon and the Ascendant. The Sun sign describes core identity and what energizes you. The Moon sign describes inner emotional life, what comforts you and how you react under stress. The rising sign describes first impressions and the approach you take to new situations. Read together, these three already say more than a Sun sign alone.
How to read a chart in five steps
- Note the big three and write one plain sentence for each.
- Count the planets in fire, earth, air and water signs. A chart heavy in one element often shows a dominant style: fire acts, earth builds, air thinks and water feels.
- Look for houses that hold several planets. A cluster in one house marks an area of life that draws much attention.
- Find the tightest aspects, those within about three degrees. These show the strongest themes and the sharpest inner tensions.
- Find the chart ruler, the planet that rules the rising sign. The sign and house of that planet show where the energy of the chart is directed.
Avoid reading any single placement alone. A chart is read as a whole, and each factor is softened or sharpened by the others.
House systems
There are several ways to divide the chart into houses, including Placidus, Whole Sign, Koch and Equal House. Placidus is the most common in modern Western astrology, and Whole Sign is popular among those who follow older traditions. The positions of planets in signs are the same in every system. Only the house boundaries change. If a planet sits close to the edge of a house, look at it in two systems before deciding.
What a chart can and cannot tell you
A chart gives a language for reflecting on temperament, patterns and timing. Scientific studies have not found that planetary positions predict personality or events, so it is wise to treat astrology as a tool for self-reflection and not as a rulebook. It cannot replace medical, legal or financial advice. Many people find the value lies in the questions a chart raises and not in any fixed answer.