Couples & Encounters
Your two skies
Compare two birth charts to see how they respond to each other: crossed aspects, house overlays, the midpoint chart, and the couple's composite chart.
What is synastry?
Synastry compares two birth charts to read a relationship between two people. Where a birth chart describes an individual, synastry describes a two-person dynamic: what each activates in the other, where the frictions and complementarities lie.
This page offers five complementary readings from the dates, times, and places of birth of both people: the crossed aspects between their planets, the overlays— one person’s planets projected into the other’s houses —, the composite chart, the Davison chart, and an element/modality compatibility score.
These five sections are currently shown in raw form — tables and figures, with no written interpretation — except for the house overlays, which come with an accessible reading in Discovery mode.
How these calculations are made
As with the birth chart, planetary positions rely on the Swiss Ephemeris. The composite is calculated by taking the geometric midpoint of each planet between the two charts; the Davison chart first establishes a real midpoint date, time, and place, then calculates a full birth chart for that instant — the house cusps there are true cusps, not averages of degrees.
No astrological rule is invented: the orbs of the crossed aspects and the sign → element/modality classification follow exactly the same conventions as the birth chart. Neither birth ever leaves the server for a third party.
Frequently asked questions
- What is synastry in astrology?
- Synastry compares two birth charts to study a relationship — romantic, friendly, professional. It overlays the planetary positions of the two people to spot resonances (crossed aspects) and the areas of life each activates in the other (planets in the other's houses).
- What are the crossed aspects between two charts?
- These are the angles (conjunction, square, trine, opposition...) formed between a planet in the first chart and a planet in the second — for example, one person's Sun conjunct the other's Moon. They work like the aspects of a classic birth chart, but between two distinct birth skies.
- What's the difference between the composite chart and the Davison chart?
- The composite chart calculates the geometric midpoint of each planet between the two charts — a purely mathematical viewpoint, with no real instant. The Davison chart, instead, calculates the midpoint date and place between the two births, then builds a true birth chart for that real midpoint moment: it's a chart calculated like any other, not an average of positions.
- What does the element/modality compatibility score mean?
- It compares the distribution of each chart's ten classical planets across the four elements (fire, earth, air, water) and the three modalities (cardinal, fixed, mutable), to show whether the two temperaments complement or resemble each other. It's a temperament indicator, not an overall relationship-compatibility score — full synastry (aspects, houses) remains the finest level of reading.
- Do you need both people's exact birth time?
- It's needed for the house overlays, the composite chart, the Davison chart, and each person's Ascendant. Without a precise time, the crossed aspects between planets remain calculable (sign positions don't depend on time), but anything involving houses or the Ascendant loses its reliability.