← Encyclopedia of Astrology · lesson 220/235
Natal chart
What it is
A natal chart, or birth chart, is a map of the sky as seen from the place of birth at the moment of birth. It shows where the Sun, the Moon and the planets stood in the zodiac, which part of the zodiac was rising on the eastern horizon (the Ascendant) and which was culminating overhead (the Midheaven), and how the sky divides into the twelve houses from there. James Lewis notes that natal astrology is the modern name for what older astrologers called genethlialogy, the astrology of births — the subject of Ptolemy's third book.
What it needs
Three facts: the date, the time and the place of birth. The date fixes the planets' signs, which change slowly; the time and place fix the angles and houses, which turn through the whole zodiac in a day — the Ascendant moves about a degree every four minutes. A birth time that is uncertain by an hour can therefore shift the rising sign and every house, while leaving most planets where they are. When the accuracy of a time is not stated, it is taken here to be within about fifteen minutes; a time that is only approximate is better read for its planets by sign than for its houses.
The place matters twice: for the latitude and longitude that set the angles, and for the time zone and daylight saving in force on that date, so the local clock time can be turned into the true moment.
What it contains
- the planets in their signs — what kind of energy, in what style;
- the planets in their houses — in which area of life;
- the aspects between them — how they combine;
- the angles and the chart ruler;
- the larger figures some of them form, such as a Grand Trine or a stellium.
How the houses are drawn depends on the house system.
How it is used
The natal chart is read as a description of temperament and potential: tendencies, gifts and tensions a person tends to carry through life. It does not fix a life in advance; it describes the material. It is also the base for every forecasting technique — transits, progressions and solar arcs are all read against it.