Two people want one chart for their bond. Astrologers hand them a composite chart. What almost no one says out loud is that a second method exists, it has its own name, and it disagrees with the first one about half the time.
We tested that claim. We paired births from sixty years of US birth times and cast both charts for each pair. The Sun landed in a different sign in 50.8 of every 100 pairs. The Moon: 57.6. The rising sign: 56.7. Those are not small gaps. They are coin flips.
This guide shows you what each chart is, how the two are built, where they split, and which one to read.
What a composite chart is
A composite chart is a chart of midpoints. Take the Sun in the first birth chart. Take the Sun in the second. Find the point halfway between them on the zodiac wheel. That halfway point is the composite Sun. Do the same for the Moon, for Venus, for Mars, for every point. You now hold a third chart.
Here is the part that gets skipped. No one was born at that moment. The composite chart is not a snapshot of the sky. It is an average. If one partner has the Sun at 10 degrees of Aries and the other at 10 degrees of Gemini, the composite Sun sits at 10 degrees of Taurus. The sky never looked like that on any day of their lives.
There is a catch built into the method. Two points on a circle have two midpoints, not one, and they sit opposite each other. Astrologers use a rule: take the near one, the one inside the shorter arc. Hold on to that rule. It is the whole reason the two charts split later.
What a Davison chart is
The Davison chart takes a different road. Instead of averaging positions, it averages the births.
Say one partner was born on 3 May 1988 in Chicago and the other on 3 May 1994 in Lisbon. Find the moment exactly halfway between the two birth times. Find the spot on Earth halfway between the two birthplaces. Then cast a normal chart for that moment and that spot.
The result is a real chart of a real sky. Someone born at that place and that hour would own it as a birth chart. That is the selling point Davison fans lean on: the chart maps a moment that actually happened.
Note what this means for house placements. The Davison chart has a true rising sign, because it has a true time and a true place. The composite chart has to fake one by averaging two rising signs.
Where the two charts split: what our test found
We wanted numbers, not opinions. So we ran the math.
The method. We set one birth about every five days from 1950 to 2009. Each birth got a US birthplace and a clock time, spread evenly in line with where Americans live and with the hours at which US babies are born in CDC records for 2024. Each birthplace kept its real time zone. Then we paired every birth with every other birth no more than 12 years away, since that fits most couples. The Davison place is the plain average of the two latitudes and the two longitudes. We used the tropical zodiac and Swiss Ephemeris for the sky positions, and ran it all again with the open-source astronomy-engine library. The two runs agree to the first decimal. For each pair we cast both charts and compared the Sun, the Moon and the rising sign.
Here is what came back.
- The Sun. In 50.0 pairs out of 100, the two Suns sat within 10 degrees of each other. In the other 50.0, they sat between 170 and 180 degrees apart. That is a straight face-off across the wheel. There was almost nothing in between.
- The Moon. Nearly the same shape. Close in 44.0 pairs out of 100, opposite in 45.8 out of 100. The last 10.2 fall in between, because the Moon speeds up and slows down along its path.
- The rising sign. Within 10 degrees in 42.9 pairs out of 100. Spread out much wider than the Sun, since the rising sign also depends on where on Earth each birth took place.
- Different sign, not just different degree. The Sun changed sign in 50.8 pairs out of 100. The Moon in 57.6. The rising sign in 56.7.
Read that last line again. For close to six couples out of ten, the two methods hand you a different rising sign. Not a shade of meaning. A different sign, a different house layout, a different story.
What we did not test. We compared the Sun, the Moon and the rising sign. We did not test the outer planets, the aspects, or the house cusps under every house system. And a chart is not a person: this is a math check on two methods, not proof that either one works.
Why the split happens
The cause is that midpoint rule, and it is simple once you see it.
The Sun walks the zodiac once a year. Suppose two people were born six years and two months apart. In that span the Sun went around the wheel six full times, plus a bit. The Davison chart follows real time, so it lands where the Sun truly was at the halfway hour. The composite chart only sees the two end positions. It cannot see the six laps in between.
So it picks the near midpoint, and that lands on the wrong side of the wheel whenever the number of laps is odd. Even number of laps: the two charts agree. Odd number: they face off across 180 degrees. Since the age gap in a couple is as likely to be odd as even, you get the coin flip we measured.
The Moon runs the same trap much faster. It circles the zodiac in under 28 days, so the laps pile up fast. The rising sign spins once a day, which is why its gap is wider and messier.
None of this is a bug in the software. Both charts are built exactly as their authors described. They are answering two different questions.
Both charts are modern. The old books have neither.
This matters, and few pages say it.
Classical astrology has no composite chart. Ptolemy does not describe one in the Tetrabiblos, in the second century. William Lilly does not describe one in Christian Astrology, in 1647. To read a bond, those astrologers laid the two birth charts side by side, or cast a fresh chart for the wedding hour. Merging two charts into a third was not part of the craft.
The midpoint idea grew out of the Hamburg School in Germany, in the early 1900s, around the work of Alfred Witte. Midpoints there were a tool for reading a single chart. Turning them into a chart of a couple came later.
The dates are worth having straight, because they get mixed up on almost every page that covers this.
- John Townley published the first book on the composite chart, The Composite Chart, in 1973.
- Robert Hand wrote Planets in Composite in 1975. It is still the book most astrologers reach for.
- Ronald Davison, a British astrologer who led the Astrological Association of Great Britain, set out the time-and-place method in 1977, in Synastry: Understanding Human Relations Through Astrology. The chart carries his name.
So the Davison chart is not a Townley idea, and it is not a variant of the composite chart. It is a rival method from a rival author, four years later.
Fifty years is young for an astrological technique. That is not a strike against it. It does mean you should hold it with open hands, and know who built it and when.
Synastry is a third thing, and it is not the same
People mix these up daily, so let us be blunt.
Synastry compares two charts. Your Venus, their Mars, the angle between them. Nothing new is built. You read how one person’s sky touches the other’s. Our guide to synastry charts and relationship dynamics walks through that method step by step.
A composite chart builds a third chart. The two people drop out of view. What is left is the bond as its own body, with its own Sun sign and its own house map.
The two answer different questions. Synastry says how you meet. The composite chart says what the two of you became. A Davison chart says the same thing in a different accent.
If the pull between two people runs through Venus, the natal Venus placements are the first thing to read. A partner with Venus in the seventh house brings a different set of needs to the table than one with Venus buried in the twelfth. Our page on the planet Venus and its role in love covers the basics in plain words.
Which chart should you read?
Our numbers do not crown a winner. They tell you that picking one is a real choice, not a shrug.
Use the composite chart when you want the tradition with the deepest bench. Fifty years of written work sit behind it. Hand’s book gives you a reading for every placement. Most software draws it by default. Most astrologers you meet were trained on it.
Use the Davison chart when you care that the chart points at a real sky. It has a true rising sign and true house cusps. It also moves in time, so you can run transits across it the way you would across a birth chart. Some astrologers read the Davison date itself as a marker for the bond.
Read both when the two disagree, which our test says will happen for the Sun in about half of all pairs. A clash between the two charts is a signal, not a problem. It tells you the pair sits at an odd number of solar laps apart, and it hands you two angles on the same bond.
What you should not do is read one, call it the truth, and never learn that the other exists.
How to check your own pair in five minutes
- Get both birth dates, both birth times, and both birth cities. Times matter here. Without them there is no rising sign in either chart.
- Draw the composite chart in any free tool. Note the Sun sign, the Moon sign and the rising sign.
- Draw the Davison chart in the same tool. Most sites offer both. Note the same three.
- Compare. If the Sun signs are opposite each other on the wheel, such as Aries and Libra, you have hit the lap effect we measured.
- Count the years between the two births. An odd count is the tell.
One more thing to watch. Some tools draw a derived composite chart, which uses the midpoint of the two rising signs. Others draw a reference-place composite chart, which pins the houses to one city. Those two give different houses from the same planets. Check which one your tool uses before you read the houses.
Frequently asked questions
Is a composite chart more important than synastry?
Neither outranks the other. Synastry reads how two people meet. A composite chart reads the bond as a thing in itself. Most astrologers open with synastry, then bring in the composite chart for the shared story.
How do I calculate my composite chart?
Take each point in both birth charts and find the halfway degree between the two, using the shorter arc. Free tools do this in one click once you enter both birth dates, times and cities.
What does a composite chart reveal about a relationship?
It shows the shape the bond takes: what it is for, where it shines, where it strains. The Sun points at the shared purpose, the Moon at the private mood, Venus and Mars at warmth and friction.
Is the Davison chart better than the composite chart?
It is not better, it is built differently. The Davison chart maps a real moment and a real place, so its houses and its rising sign come from an actual sky. The composite chart has more written material behind it. Our test found they name a different Sun sign in 50.8 pairs out of 100.
Why do my composite and Davison Suns sit opposite each other?
Because the Sun made an odd number of full laps between the two births. The composite method takes the nearer of the two possible midpoints, and with an odd lap count the nearer one lands on the far side. We saw this in 50.0 pairs out of 100.
Do composite charts work for friends and business partners?
Yes. Robert Hand and John Townley both apply the method to any bond between two people. The chart maps a shared field, not romance alone.
Where this leaves you
The composite chart is a fine tool with a clear history and a real limit. It averages two skies and calls the result a third one. The Davison chart takes the other road and points at a sky that truly happened. In half of all pairs, they say opposite things about the Sun.
Learn both. Draw both. When they line up, you have a strong signal. When they clash, you have learned something about the gap between two lives, in years and in miles.