A real moment for the relationship
A Davison chart treats a relationship the way a birth chart treats a person: as something born at a moment and a place. The English astrologer Ronald Davison introduced it in his 1977 book Synastry. It is cast for the instant halfway between two people's births, at the place halfway between their birthplaces. If one of you was born in London in January 1980 and the other in New York in July 1990, the chart is cast for April 1985, over the middle of the Atlantic.
Because that moment really happened, every planet is where it actually was, the aspects are real aspects, and the chart can be progressed and followed by transits just like a birth chart. It works for any pair: partners, friends, family, business partners. The calculator doesn't give a compatibility score; it shows the chart and what astrologers read first.
Davison or composite?
The composite chart, the other standard relationship chart, takes the midpoint of each pair of planets instead. That is simpler, but the result is not a sky that ever existed. In 1,500 random pairs of birth charts from 1950 to 2009, with birth times, the composite put Mercury more than 28° or Venus more than 48° from the Sun in 13% of pairs, farther than either ever strays in a real sky; the Davison chart never does. The two charts also disagree more than people expect: the Davison and composite Suns fell in the same sign in only half of the pairs, and the Moons in 43%.
| Composite | Davison | |
|---|---|---|
| Built from | The midpoint of each pair of planets | The sky at the moment and place halfway between the births |
| A real sky | No | Yes |
| Houses | From the composite Midheaven at a chosen latitude | From that moment and place, like any chart |
Many astrologers read both. The composite chart calculator builds the other one, and the synastry chart compares your two charts point by point.
What to read first
- The Sun: what the relationship is for. Its house shows the area of life it centers on: the 5th for romance and fun, the 10th for a shared public life or work, the 4th for home and family.
- The Moon: what the relationship needs to feel safe and how it handles feelings.
- Venus: how affection is shown and what you enjoy together.
- The Ascendant: how you come across as a couple.
- The aspects: flowing ones (trines and sextiles) are read as ease, challenging ones (squares and oppositions) as friction that asks for work.
Astrologers also follow transits to the Davison chart, which can time the relationship's chapters.
Use the Davison aspects filters to find a planet or a specific pair. Each result shows both positions and the orb; Show more aspects reveals the rest. Printing includes every matching aspect. Switching between the two Davison versions recalculates the list and clears its filters.
Copy for my AI copies the Davison version currently shown, including every planet and all calculated aspects before filters. It names the selected method and lunar node, and the actual house system and angle houses. Birth details and the derived midpoint time and coordinates are left out. Copy, image and print actions stay available when you switch methods.
Two versions of the chart
Davison calculators don't all agree, for two reasons. The first is the moment. The plain version is cast for the exact midpoint in time. The corrected version, which astro.com calls the classical method and uses by default, moves that moment until the Midheaven equals the composite Midheaven, the midpoint of the two natal Midheavens. In the same sample the two versions either nearly agreed or were far apart: for 49% of the pairs the corrected moment was within half an hour of the midpoint, and for the other 51% it was 11 to 12 hours away, which moved the Moon by 6.5° on average and turned the Midheaven to the opposite side of the chart, moving the Ascendant and houses with it. The switch above the wheel shows both.
The second is the place. The calculator averages the two birthplaces' latitudes and their longitudes (the shorter way round the globe), the customary method. Some programs use the great-circle midpoint instead, the true halfway point along the shortest route, which for distant birthplaces can lie far to the north, even near the pole, where house systems break down.
How it is worked out
The moment is the instant halfway between the two births in Universal Time, so time zones don't shift it. The planets come from the site's own ephemeris, the same one behind every chart here, and the houses follow Chart settings (Placidus by default). Without both birth times the midpoint moment can be off by hours, so the Moon is only approximate and the Ascendant, Midheaven and houses are left out. Your details stay in your browser.