A map of the sky as it was at the exact moment and place of birth.
It is computed from three pieces of information: date, time and place. From these come the planets' positions in the signs, the division into houses, and the aspects between bodies. The name enters no calculation — it belongs to numerology, not astrology.
What you see on the wheel
A birth chart is usually drawn as a wheel. The outer ring carries the twelve signs; inside it, lines divide the space into the twelve houses, numbered anticlockwise from the Ascendant on the left. The symbols around the wheel are the planets, each at its degree, and the coloured lines in the middle that join them are the aspects: the meaningful angles between one planet and another.
Four lines stand out: the Ascendant, Descendant, Midheaven and Imum Coeli, known as the angles. The lower half of the wheel is the sky below the horizon, the upper half the visible sky, so a Sun near the top means a daytime birth and a Sun near the bottom a night-time one.
Where to start reading it
A simple order helps. Begin with the big three: your Sun sign, your Moon sign and your Ascendant, which together sketch identity, emotional life and the way you present yourself. Then look at the houses they fall in, which show the areas of life where these play out.
Next come the aspects, starting with the tightest, those with the smallest orb, which astrologers weight most heavily. Last, step back and look at the overall distribution: whether many planets gather in one sign, one house or one half of the wheel. Every element is read alongside the others, because no single placement ever describes a whole person.
Frequently asked questions
How can I get my birth chart for free?
You need your date, time and place of birth. On SideraMea the birth chart is free: you get the wheel, planetary positions, houses, aspects and a basic reading. It is calculated with the Swiss Ephemeris and your birth time is converted to Universal Time, allowing for the time zone and daylight saving.
Does your birth chart change over time?
No. It is a snapshot of the sky at one precise moment, and it stays the same for life. What changes is today's sky in relation to that snapshot. Transits study this by comparing the current planets with those at birth, and progressions, a symbolic technique, move the chart forward through time.
How accurate does my birth time need to be?
The more precise, the better. For planets in signs a rough time is usually enough, unless the Moon or a planet is close to changing sign. For the Ascendant, Midheaven and houses, minutes count: a quarter of an hour out can move the Ascendant by a few degrees. The time on your birth certificate is usually the most reliable source.
See it in your own chart
Calculating your birth chart is free: wheel, planets, houses, aspects and a first reading. All you need is your date, time and place of birth.