Which is better, a Davison or a composite chart?

Neither, and anyone who tells you otherwise is stating a preference. The composite is more widely used and easier to reproduce; the Davison is a real chart and can be progressed and transited like any other. Run both, and pay attention to where they agree.

Why is the Davison Moon so different from the composite Moon?

Because the Moon moves fastest. A composite Moon is the midpoint between two Moons, which is arithmetic; a Davison Moon is where the Moon actually was at the midpoint instant. With two births years apart those can be signs apart, and this is the placement where the two methods most often part company.

Can a Davison chart be cast for three people?

The method extends to any number of births by averaging all their instants and all their positions, and some astrologers do it for families or bands. This tool handles pairs only, which is where the technique is on firm ground.

Do we both need our birth times?

For the planets, no. For the houses, yes, both of them: the midpoint of one exact instant and one noon guess is itself a guess, off by up to six hours, and an Ascendant computed from that would be fiction. The tool drops the houses rather than printing them.

Does the midpoint place mean anything?

It is where the chart is cast, and nothing more. It is often somewhere neither person has been, which is a good reminder that the point is a calculation rather than a destination.

Free tool

Davison Chart Calculator

A Davison chart is an ordinary chart cast for an extraordinary moment: the instant exactly halfway between two births, at the place exactly halfway between two birthplaces. Somebody could have been born then and there. This is the chart they would have.

Enter both people's birth data

Person A

Birth Date

Birth Time

I don't know my birth timeBirth City

Enter coordinates manually

Your birth details are used only to calculate this chart. They are not saved.

Person B

Birth Date

Birth Time

I don't know my birth timeBirth City

Enter coordinates manually

Your birth details are used only to calculate this chart. They are not saved.

Still needed:Person A: Birth Date · Birth Time · Birth CityPerson B: Birth Date · Birth Time · Birth City

What a Davison chart is

Take two birth moments and find the instant halfway between them. Take two birthplaces and find the point halfway between them on the surface of the Earth. Cast a chart for that time at that place. That is a Davison relationship chart, named after Ronald C. Davison, who set the method out in the middle of the twentieth century. Because it is a real chart for a real moment, everything a birth chart has, it has: planets with retrograde motion, houses from a real horizon, a Moon that was genuinely at that degree. It can be read with ordinary chart technique, and it can even be progressed or transited, which is the main practical argument its users make for it.

Davison or composite? Both, and they disagree

The two methods answer the same question and give different degrees, sometimes different signs. A composite chart averages two charts into a construct: each composite planet is the midpoint between the same planet in the two charts, and the result is a set of positions that no sky ever held. A Davison chart is the sky, at one moment, from one place. Neither is more correct. The composite is symmetrical, portable and instantly reproducible; the Davison is a real event with real houses and real motion. Astrologers who use both usually look for what the two agree on. What we can do here is show you both and refuse to quietly pick one for you.

Calculate the composite chart

Read the guide to relationship charts

Compare the two charts directly with synastry

How the midpoint is found

The midpoint in time is the plain average of the two birth instants in Universal Time, which needs no cleverness: time runs in one direction and a halfway point is a halfway point. The midpoint in space does need care. Averaging two longitudes as numbers is wrong near the date line: 179° east and 179° west are two degrees apart, but their arithmetic mean is 0°, a quarter of the planet away in the Gulf of Guinea. So both places are converted into points on a sphere, the two points are averaged, and the result is projected back to a latitude and longitude. Away from the wrap this agrees with the simple average; across it, it gives the point actually between the two. The one case with no answer is a pair of exactly antipodal birthplaces, where every point on the connecting circle is equidistant, and the tool says so rather than inventing a location.

What this is not

It is not a verdict on a relationship and there is no score in it. A Davison chart is one more frame for looking at a pair of lives, computed exactly, meaning nothing on its own. Two people are not the geometry between their birth certificates, and no arrangement of degrees on this page knows anything about how they treat each other.

Questions about Davison charts

Which is better, a Davison or a composite chart?: Neither, and anyone who tells you otherwise is stating a preference. The composite is more widely used and easier to reproduce; the Davison is a real chart and can be progressed and transited like any other. Run both, and pay attention to where they agree.
Why is the Davison Moon so different from the composite Moon?: Because the Moon moves fastest. A composite Moon is the midpoint between two Moons, which is arithmetic; a Davison Moon is where the Moon actually was at the midpoint instant. With two births years apart those can be signs apart, and this is the placement where the two methods most often part company.
Can a Davison chart be cast for three people?: The method extends to any number of births by averaging all their instants and all their positions, and some astrologers do it for families or bands. This tool handles pairs only, which is where the technique is on firm ground.
Do we both need our birth times?: For the planets, no. For the houses, yes, both of them: the midpoint of one exact instant and one noon guess is itself a guess, off by up to six hours, and an Ascendant computed from that would be fiction. The tool drops the houses rather than printing them.
Does the midpoint place mean anything?: It is where the chart is cast, and nothing more. It is often somewhere neither person has been, which is a good reminder that the point is a calculation rather than a destination.

The conventions this chart uses

None of these are facts of the sky. Each is a choice astrologers disagree on, so we list ours — a difference from another site can then be traced to its rule instead of blamed on the stars.

Tropical zodiac: Signs are tropical, anchored to the March equinox, not to the constellations. Sidereal (Vedic) astrology counts from the stars instead, which currently shifts every position by about 24 degrees — the most common reason two sites disagree about a sign.
Placidus houses: Houses are Placidus, the most widely used modern system. Whole-sign or Koch redraw the boundaries: they move planets between houses, never between signs. Beyond the polar circles Placidus is undefined, and we then show the chart without houses rather than guess.
Mean lunar nodes: The lunar nodes are mean (averaged). The "true" node oscillates around the mean by up to about two degrees — measured, at most 1°59' across two centuries.
Mean Lilith: Black Moon Lilith is the mean lunar apogee. The "true" (osculating) variant can sit up to about thirty degrees away — often a different sign, and the single biggest source of Lilith disagreements.
Aspect orbs: Natal orbs: conjunction and opposition 8°, square and trine 7°, sextile 5°, quincunx 3°. Toward the Ascendant and Midheaven the orbs tighten, and the quincunx is not counted there at all. A site with wider orbs lists more aspects, not different planets.
Sect: The Part of Fortune follows sect: a day birth (Sun above the horizon) uses Ascendant + Moon − Sun, a night birth the reverse. For night births, calculators that apply the day formula to everyone place it in a different sign roughly nine times out of ten.