How to read your birth chart wheel

The wheel is a snapshot of the sky from where you were born, at the moment you were born. By convention, the eastern horizon sits on the left: that's the Ascendant (AC), the sign that was rising at that exact moment. Opposite, on the right, is the Descendant. At the top sits the Midheaven (MC), the highest point of the sky; at the bottom, its opposite, the Imum Coeli.

From the Ascendant, the zodiac runs anticlockwise. These two axes, horizon and meridian, are the backbone of the chart: they're drawn more boldly on the wheel, and they depend on your time of birth to the minute.

The outer ring carries the twelve signs, each spanning 30°, with a scale of degrees all around. Each sign belongs to an element, fire (Aries, Leo, Sagittarius), earth (Taurus, Virgo, Capricorn), air (Gemini, Libra, Aquarius) or water (Cancer, Scorpio, Pisces), shown by a discreet tint on the wheel.

A sign describes a way of being, a style. On its own it says little: it's the planet sitting in it that gives it something to express.

Inside the signs, twelve sectors numbered 1 to 12: the houses. Where the signs say “how”, the houses say “where”: identity, resources, close relationships, home, creativity, daily life, partnership, intimacy, horizons, vocation, friendships, inner life.

The houses come from your exact time and place of birth, so two people born on the same day in different cities don't have the same houses. Filigra uses the Placidus system, the most widespread; beyond the polar circles, where it isn't defined, it switches to the Porphyry system.

Around the wheel sit the planets, each with its glyph and its precise position: for example, 10°46′ means 10 degrees and 46 minutes into the sign. When several planets are close together, their glyphs are spread apart and a thin line points to their exact place on the ring.

An “R” marks a retrograde planet: seen from Earth, it seems to move backwards for a while. It's an optical effect, traditionally read as an energy turned more inwards. The Sun and the Moon are never retrograde; the lunar nodes and Lilith have their own motion, which is why the “R” isn't shown for them.

The lines across the centre connect planets that form a significant angle: these are the aspects. The tensions (square at 90°, opposition at 180°) are drawn in plain red; the harmonies (trine at 120°, sextile at 60°) in dashed blue; the quincunx (150°), a subtler adjustment, in dotted green. Conjunctions, two planets side by side, need no line.

An aspect allows a small margin, the orb, shown in the aspects table: the tighter the orb, the more the aspect counts. Tap a planet on the wheel and only its aspects stay lit.

Beyond the ten planets, a few points complete the picture. Chiron speaks of a sensitive wound and the gift it makes possible. The North and South Nodes, always facing each other, describe a direction of growth and the familiar ground you come from. Lilith (the Black Moon) points to the untamed part of you. The Part of Fortune, calculated from the Sun, Moon and Ascendant, marks a point of ease.

The asteroids (Ceres, Pallas, Juno, Vesta) and the Vertex are available as an option, for those who want to go further.

Filigra calculates positions with Swiss Ephemeris, based on NASA's JPL ephemerides, in the tropical zodiac. The historical time zone and daylight saving time in force at your birth are deduced from the place, a frequent source of errors elsewhere. No AI is involved in the calculation.

Uranus, Neptune and Pluto stay several years in the same sign: their sign describes a generation more than a person, and their house gives the personal touch. And above all, a chart describes inclinations, never a destiny: it's a tool for reflection, not a prediction.