Guides / Relationship astrology
What is synastry?
Synastry compares two natal charts by the aspects between them, and, in the Vedic layer, by Ashta Koota from the two Moons.
Two charts in conversation
Synastry is the comparison of two birth charts. Each person’s planets stay in their own signs. The question is how those planets aspect one another: whether one person’s Moon sits on the other’s Sun, whether Mars squares Venus, whether the Ascendants support or tense each other.
Astrologers look at those aspects because they describe contact. A trine between two Moons is a different climate from a square between one person’s Mercury and the other’s Pluto. The aspect names the kind of contact; the planets name the subjects.
What Inner Light compares
The synastry page calculates two tropical natal charts and lists the major aspects between them, with angle and orb. When both birth times are known, house overlays can appear in that table, Ashta Koota can be scored from the two Moons, and each Vedic D1 chart can include a Mangal Dosha count.
Moon-to-Moon and Ascendant-to-Ascendant contacts come first: they describe emotional climate and the way two people meet the world together. They are still aspects among others, not a single compatibility score.
Common questions
- What are house overlays?
- A house overlay is one person’s planet falling in the other person’s house. It requires both birth times, because houses are counted from each Ascendant.