A natal chart, also called a birth chart, is a diagram of the sky at the moment a person was born: where the sun, the moon and the visible planets stood against the twelve signs of the tropical zodiac, seen from the place of birth at the hour of birth. Western astrology reads that diagram as a portrait of temperament, built from three vocabularies at once, which planet, in which sign, and in which house of the chart.

History

The practice begins in Babylon, where scribes had read the sky as a set of omens for the state and the king since at least the second millennium BCE, recorded in long omen series such as Enuma Anu Enlil. Horoscopic astrology, a reading tied to one person's exact moment of birth rather than to the fortunes of a kingdom, is later: it appears once Babylonian astronomers had fixed a zodiac of twelve equal thirty degree signs, by around the fifth century BCE.

The system a natal chart still uses today took shape in Hellenistic Alexandria from roughly the second century BCE, where Babylonian celestial reckoning met the Egyptian tradition of decans, the ten degree sub-divisions of each sign, and Greek philosophy's idea of a cosmos bound together by sympathy between the heavens and the earth. The houses, the aspects between planets and the dignity system that judges a planet strong or weak in a given sign all come from this synthesis. The Tetrabiblos, attributed to the astronomer Claudius Ptolemy in the second century CE, became its standard reference text.

Astrology travelled into the medieval Islamic world, where astronomer-astrologers such as Abu Ma'shar in ninth century Baghdad preserved, translated and expanded the Hellenistic corpus, and from there into Latin Europe through twelfth century translation centres including Toledo. For several centuries afterward it sat inside ordinary learning, taught alongside astronomy, medicine and philosophy at European universities through the Renaissance.

Its standing as a scholarly discipline did not survive the Copernican and Newtonian revolutions, which by the seventeenth and eighteenth centuries had split astronomy from astrology into two separate pursuits, one kept and one set aside. Astrology persisted as a popular and esoteric practice rather than an academic one, and its modern shape owes most to two later moments: Alan Leo's newspaper sun-sign columns in the early twentieth century, which popularised a simplified single-sign astrology for a mass readership, and a separate turn toward psychological and symbolic interpretation later in the century, closer to how a full natal chart reading is generally practised today.

The Planets

Ten bodies carry the weight of a natal reading: the sun and the moon, called the luminaries, and eight planets running outward from Mercury to Pluto. Each is read as governing its own department of a life, and its sign and house say how and where that department shows itself.

• The Sun, core identity and vitality.
• The Moon, feeling, habit and the inner emotional life.
• Mercury, thought, speech and how information is gathered.
• Venus, attraction, taste and what is valued.
• Mars, drive, assertion and how conflict is met.
• Jupiter, expansion, confidence and where growth is sought.
• Saturn, structure, restriction and where discipline is required.
• Uranus, sudden change and independence.
• Neptune, imagination, dissolution and idealism.
• Pluto, transformation, and what is buried and later surfaces.

A planet is never read alone. Its sign colours how it acts, its house says where in life it acts, and its aspects to the other planets say whether that action comes easily or under tension.

The Zodiac Signs

The tropical zodiac divides the year, not the visible stars, into twelve thirty degree signs beginning at the spring equinox. The twelve, in order, are Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces, and each carries an element, fire (Aries, Leo, Sagittarius), earth (Taurus, Virgo, Capricorn), air (Gemini, Libra, Aquarius) or water (Cancer, Scorpio, Pisces), and a mode, cardinal, fixed or mutable, that together describe a kind of energy rather than a fixed personality type.

The oldest layer of the system survives inside each sign as well: the Babylonian and Egyptian decans split every thirty degree sign into three ten degree bands, each with its own planetary ruler, which is one reason two people born three weeks apart under the same sign can still read differently. A planet's dignity, whether a sign strengthens or weakens it, comes from a related pairing: a planet in the sign it rules, called its domicile, or in the sign ancient astrologers held it to act at its best, its exaltation, is read as strong, and in the opposite sign as weak.

The Houses

Where the signs say what kind of energy a planet carries, the twelve houses say which department of life it falls in, running counter-clockwise from the eastern horizon at the moment of birth. The first house begins at the ascendant, the exact degree rising in the east at the birth hour, and the rest follow it around the wheel.

• 1st House, the self and how a person meets the world.
• 2nd House, possessions and personal resources.
• 3rd House, communication and the immediate community.
• 4th House, home, family and roots.
• 5th House, creativity, romance and children.
• 6th House, work, health and daily routine.
• 7th House, partnership and open conflict.
• 8th House, shared resources, loss and transformation.
• 9th House, belief, travel and higher learning.
• 10th House, vocation and public standing.
• 11th House, community and long range goals.
• 12th House, the unseen, solitude and what is given up.

How A Reading Is Constructed

A reading starts from three pieces of data: the date, the exact time and the place of birth. From those, an ephemeris, a table of planetary positions, gives the degree of every planet at that moment, and the birth time and place fix the houses by one of several house systems in use today, most commonly Placidus. A birth time even a few minutes off can move a planet from one house to the next, which is why the hour matters nearly as much as the day.

The wheel is then read for aspects, the angles between planets: a conjunction, planets at the same degree, blends their energies; a trine and a sextile read as ease; a square and an opposition read as tension the chart has to resolve. An astrologer works outward from the sun, the moon and the ascendant, the chart's three central points, then layers in each planet's sign, house, dignity and aspects, and reads the whole as one portrait rather than as twelve separate sentences. Colours, stones and herbs traditionally held to belong to each planet or sign are often folded in as a further layer of correspondence, the same associative logic that runs through the rest of Western esoteric practice.

Where To Read More

• SunPlanetsThe Sun: core identity and vitality.
• MoonPlanetsThe Moon: feeling, habit and the inner emotional life.
• MercuryPlanetsMercury: thought, speech and how information is gathered.
• VenusPlanetsVenus: attraction, taste and what is valued.
• MarsPlanetsMars: drive, assertion and how conflict is met.
• JupiterPlanetsJupiter: expansion, confidence and where growth is sought.
• SaturnPlanetsSaturn: structure, restriction and where discipline is required.
• UranusPlanetsUranus: sudden change and independence.
• NeptunePlanetsNeptune: imagination, dissolution and idealism.
• PlutoPlanetsPluto: transformation, and what is buried and later surfaces.
• AriesAries: the first sign, cardinal fire.
• TaurusTaurus: fixed earth.
• GeminiGemini: mutable air.
• CancerCancer: cardinal water.
• LeoLeo: fixed fire.
• VirgoVirgo: mutable earth.
• LibraLibra: cardinal air.
• ScorpioScorpio: fixed water.
• SagittariusSagittarius: mutable fire.
• CapricornCapricorn: cardinal earth.
• AquariusAquarius: fixed air.
• PiscesPisces: mutable water, the last sign.
• 1st House1st House: the self and how a person meets the world.
• 2nd House2nd House: possessions and personal resources.
• 3rd House3rd House: communication and the immediate community.
• 4th House4th House: home, family and roots.
• 5th House5th House: creativity, romance and children.
• 6th House6th House: work, health and daily routine.
• 7th House7th House: partnership and open conflict.
• 8th House8th House: shared resources, loss and transformation.
• 9th House9th House: belief, travel and higher learning.
• 10th House10th House: vocation and public standing.
• 11th House11th House: community and long range goals.
• 12th House12th House: the unseen, solitude and what is given up.
• ConjunctionMajor AspectsConjunction: planets at the same degree, blending their energies.
• TrineMajor AspectsTrine: a 120 degree angle, read as ease.
• SquareMajor AspectsSquare: a 90 degree angle, read as tension the chart has to resolve.
• Decan 1 of AriesAriesOne of the thirty-six ten degree decans a sign is split into, each with its own planetary ruler.
• Decan 2 of TaurusTaurusA second decan, showing the same sign-within-a-sign division at a different degree band.