Astrology concepts: understanding the zodiac and the chart
Fifteen concepts for understanding what astrology calculates and what it assumes: the sky and the zodiac, the signs, the birth chart.
- astrology concepts
- zodiac
- birth chart
By Thomas Guilhot · updated
The concepts at a glance
Astrology concepts are the fourteen basic reference points of the zodiac and the birth chart, presented with their history and the debates between schools.
- Concepts
- 14, each with its own page
- Families
- The sky, the signs, the chart
- Sources
- 39, from Antiquity to today
- Bridge
- Numerology and astrology
The sky, the signs, the chart
Behind a sign or a chart, there are method choices that websites rarely show: which zodiac, which house system, which orb. This section explains them one by one. Each concept opens with a one-sentence definition, then gives the exact explanation, the history, and the positions of the schools, without naming a winner.
One point up front: the astronomy underneath, the positions of the planets, is a precise calculation. The interpretations, by contrast, belong to a symbolic tradition that science has never validated. Every page cites its sources, so that you can check them.
The sky and the zodiac
Zodiacs, precession, constellations, Ophiuchus, retrograde motion, and nodes: what the sky actually does, before any interpretation.
5 conceptsThe signs
Elements, modalities, polarities, rulerships, and dignities: the categories that sort the twelve signs and their planets.
5 conceptsThe chart
Houses, orbs, angles, and minor aspects: the settings that make a birth chart vary from one website to another.
4 conceptsTwenty-five centuries of sources
The names that recur in the concepts’ sources, in chronological order. Each page cites the work and the passage.
- 5th century BCEEmpedoclesThe four elements
- around 130 BCEHipparchusThe precession of the equinoxes
- 1st centuryManilius, Dorotheus of SidonThe angles, the triplicities
- 2nd centuryPtolemy, Vettius ValensTetrabiblos, Almagest; Anthology
- 1543CopernicusRetrograde motion explained
- 1619KeplerNew aspects
- 1647William LillyDignities and orbs
- 1657Placidus de TitisThe houses that bear his name
- 1930International Astronomical UnionThe 88 constellations
- 1961André BarbaultModern French astrology
Numerology and astrology
Your sign, your life path, and your Chinese zodiac animal, calculated together from your date of birth, with the traditional correspondences between planets and numbers.
The bridge between the twoFrequently asked questions about astrology concepts
Where should I start to understand astrology?
Start with the sky: the difference between the tropical and sidereal zodiacs, then the precession of the equinoxes, gives you the framework. Move on to the elements and modalities, which structure the signs, before tackling house systems and orbs. Each page links to two or three neighboring concepts.
Is astrology a science?
No. The positions of the planets can be calculated with great precision, and that is astronomy. But no study has shown that these positions tell you anything about character or the future: controlled tests, including the one published in the journal Nature in 1985, showed no effect. Versana presents astrology as a symbolic tradition, to be read with perspective, and promises no predictions.
Why don’t all astrologers agree?
Because no authority settles the question: astrology is a tradition that has branched into schools. Tropical or sidereal zodiac, house system, orbs, modern planets or not: each of these choices changes the result. The pages in this section lay out these disagreements rather than hide them.
What are the sources of Western astrology?
It draws on Mesopotamian astronomy, then on Hellenistic Greek astrology: Ptolemy and his Tetrabiblos, Vettius Valens, Dorotheus of Sidon, Manilius. Then come William Lilly in 1647 and, for France, André Barbault. Each concept cites its precise sources at the bottom of the page.