What a birth chart shows
A birth chart — also called a natal chart or horoscope — is a drawing of the sky as seen from the place you were born, at the minute you were born. It records three things: where each planet stood in the zodiac, how the planets were angled to one another, and how the sky was turned relative to the horizon at that moment. The first two are the same for everyone born within an hour or so; the third, the rotation of the sky, turns through a full sign in about two hours and is what makes a chart personal.
Astrologers read the chart as a description of temperament and circumstance rather than a script. The positions here are tropical (measured from the spring equinox, the Western convention) and geocentric — the sky as seen from Earth.
How to read the wheel
The wheel is drawn to scale. The outer ring holds the twelve signs, each 30° wide, running counter-clockwise. The horizontal line on the left is the Ascendant, the degree of the zodiac rising in the east when you were born; the dashed line is the Midheaven (MC), the highest point the ecliptic reaches. The inner ring is divided into the twelve houses, numbered counter-clockwise from the Ascendant; the heavier lines are the cusps of the 1st, 4th, 7th and 10th houses.
Each planet sits at its exact degree, with that degree written beside its glyph and an R when it was retrograde. Planets that crowd together are stepped inward so they stay readable. The coloured lines between the planets (the node aside) are the major aspects — the conjunction, sextile, square, trine and opposition — drawn when two planets are within the usual orbs: 8° for the conjunction, opposition and trine, 7° for the square, 6° for the sextile, and 2° more when the Sun or Moon is involved. Blue lines are the easy aspects, red the hard ones, gold the conjunctions.
Planets, signs and houses in the table
The table under the wheel lists the Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto and the North Node with its position (degree, minute and sign), the house it falls in, its essential dignity and its daily speed. Dignity is the traditional measure of how well a planet is placed by sign: in its own sign (domicile) or exaltation it is strong; in its detriment or fall it is weak. A negative speed means the planet is retrograde — apparently moving backwards against the stars.
The North Node is the true node, the point where the Moon’s orbit crosses the ecliptic heading north; the South Node lies exactly opposite.
House systems: Placidus, Whole Sign, Equal
The planets don’t depend on the house system; only the house lines do. Placidus, named after the 17th-century monk Placidus de Titis and spread by printed tables in the 19th century, divides into thirds the time each degree of the zodiac takes to travel from the horizon to the meridian; it is the default in most modern Western software. Whole Sign houses, the oldest system, make the rising sign the whole 1st house, the next sign the 2nd, and so on. Equal houses run 30° each from the exact degree of the Ascendant.
Placidus can’t be calculated above about 66° latitude, where some degrees of the zodiac never rise. For births that far north or south the calculator shows Equal houses and says so.
Sun, Moon and rising sign
Most people know their Sun sign, the sign the Sun was in on their birthday. Astrologers give as much weight to two more points: the Moon, which describes the emotional life and changes sign every two and a half days, and the rising sign (the sign of the Ascendant), which describes manner and approach and changes about every two hours. The notes under the chart give a short traditional reading of each — a starting point, not a verdict. If you prefer the Vedic view, switch the chart to Vedic: it shows the sidereal positions (Lahiri ayanamsa), whole-sign houses from the Lagna, nakshatras and the current Vimshottari dasha.
From your birth chart to a question
A birth chart describes a life. Horary astrology does something narrower: it casts a chart for the moment a question is asked and reads the answer from that chart alone — the question has its own “birth”. The AstroGPT app works in this way: your question gets its own chart, cast for the minute you start a chat and ask it, at the place you are, and the reading comes from that chart rather than from your birth chart. To see how a horary chart is read, start with the horary astrology guide.
Everything here is offered for reflection and entertainment.