Composite Chart vs Synastry: What's the Difference?

The difference is what each one reads: synastry places two birth charts side by side and reads the contacts between them, how you affect them and how they affect you, while a composite chart blends both charts into a single new chart, built from midpoints, that describes the relationship as its own thing. Both are ways to read the same relationship.

Think of it as two people and the space between them. Synastry is the two people: your Moon meeting their Saturn, their Venus warming your 5th house. The composite is the space: the shared mood of the friendship, the marriage or the sibling bond, the thing you both talk about as "us". A third method, the Davison chart, describes that space differently again. All three are useful, and they answer different questions.

What synastry shows

Synastry shows how two people experience each other, contact by contact. You overlay one chart on the other and look at the aspects between planets, for example your Venus trine their Mars or your Moon square their Mercury, and at where each person's planets fall in the other's houses.

Because it keeps both charts intact, synastry stays personal and two-sided. It can show that you find them calming while they find you exciting, or that one of you feels the pull more strongly. That asymmetry is often the most useful part. A best friend who feels like family to you may experience you as their most inspiring friend, and synastry shows both halves.

Synastry is also the oldest of the three. Ptolemy compared the Sun, Moon and Ascendant of two charts in the 2nd century to judge marriages and friendships. The synastry guide walks through the method, and house overlays add the "where in life" layer.

What a composite chart shows

A composite chart shows the relationship as a single entity with its own character. The astrologer John Townley introduced it in 1973, and Robert Hand made it widely known with Planets in Composite in 1975.

It is built by taking the midpoint of each pair of matching planets, measured along the shorter arc between them. The midpoint between your Sun and their Sun becomes the composite Sun, the midpoint between your Moons becomes the composite Moon, and so on for every planet. If your Sun is at 10° Aries and theirs is at 20° Gemini, the composite Sun falls at 15° Taurus. For the houses, many astrologers follow Hand: they take the midpoint of the two Midheavens and calculate the Ascendant and houses from it for the place where the couple lives. Others take the midpoint of each pair of house cusps.

The result reads like a birth chart for the bond. A composite Sun in the 10th describes a relationship that is visible and goal-driven, the couple who build a business or the siblings everyone knows as a team. A composite Moon in the 4th describes a bond centred on home and family. Astrologers also follow transits to the composite to see when the relationship as a whole is under pressure or opening up.

Townley himself described the composite as a mathematical construct of mutual midpoints rather than a real horoscope. Because each midpoint is calculated separately, a composite can show placements that never occur in a real sky, such as Mercury opposite the Sun. Composite readers treat these as part of the relationship's signature.

What a Davison chart shows

A Davison chart is the composite's close relative, with one important difference: it is a real chart. Ronald Davison, who presented it in his 1977 book Synastry, found the midpoint in time between two births and the midpoint in place between the two birthplaces, then cast an ordinary chart for that moment and location.

Say one person was born on 1 March 1990 in London and the other on 1 March 1994 in Rome. The Davison chart is cast for about 1 March 1992, at a point roughly halfway between the two cities. Because it is an actual sky, its planets keep their real relationships, retrogrades included, and it can be progressed and followed by transits like a birth chart.

Astrologers disagree on which to use. Townley, as the composite's originator, argued the Davison chart lacked a compelling track record; Davison's followers value it precisely because it is a real moment. In both charts, Saturn and the outer planets usually land in nearly the same place. The Sun, Moon, inner planets and angles can differ a great deal.

What each one answers

Synastry, the composite and the Davison chart answer different questions, so the choice depends on what you want to know.

Synastry answers:

• Why do I feel this way around them?
• What do I bring out in them, and what do they bring out in me?
• Where do we click easily, and where do we rub?
• Why does this feel more intense for one of us?

A composite or Davison chart answers:

• What is this relationship like as a whole?
• What is it for, and what does it naturally build?
• What mood do other people see when we are together?

Synastry speaks to each person. The composite and Davison charts speak about the pair. The trade-off is that a single relationship chart loses track of who brings what. A composite Moon in Scorpio does not tell you which of you supplies the intensity, and synastry does.

Which to start with

Start with synastry. Almost every question people bring to a relationship reading is really about two people meeting: why this person, why this feeling, why this argument again. Synastry answers those directly, in terms of your actual placements. It also builds on what you already know. If you know your Venus sign and your Moon, you can follow a synastry reading straight away.

Experienced astrologers usually work in this order:

1. Each person's own chart, for how they approach relationships.
2. Synastry, for how the two of them meet.
3. A composite or Davison chart, for the character of the relationship itself.
4. Transits, for timing.

A composite reading makes more sense once you know how each person experiences the other, because the bond's overall mood is made of those individual contacts. That is why a Celestio compatibility report reads the two charts together, contact by contact: how two specific people meet is where understanding a relationship begins.

How to read a synastry reading first

A good synastry reading moves from the strongest contacts outward. If you are reading your own, this order keeps it clear:

1. Start with the Venus and Mars contacts for attraction, affection and energy.
2. Read the Sun, Moon and Ascendant contacts for identity, emotional comfort and first impressions.
3. Look at Mercury for how you talk, plan and argue.
4. Read the squares and oppositions, and any Saturn or Pluto contacts, as the places that ask for work.
5. Read the trines, sextiles and Jupiter or Saturn support as the parts that hold you together.
6. If both birth times are known, add house overlays to see where each contact is felt.

This order works for partners, a crush, friends and family alike. The long-term synastry aspects guide shows which contacts tend to hold up over years.

Frequently asked questions

Is a composite chart or synastry more accurate?

Neither a composite chart nor synastry is more accurate; they measure different things. Synastry reads two real birth charts and the contacts between them, so it describes how each person experiences the other. A composite chart is a calculated midpoint chart that describes the relationship as a unit. Most astrologers read synastry first, then add a composite for a view of the bond as a whole.

What is the difference between a composite and a Davison chart?

A composite chart is built from the midpoints of each pair of planets, calculated one by one, so it is a mathematical chart rather than a real sky. A Davison chart is a real chart cast for the midpoint in time and the midpoint in place between two births. Both describe the relationship as a single entity. As a real moment in the sky, the Davison chart can be progressed like a birth chart; progressing composites has been tried, with disputed results.

Do composite charts need birth times?

Composite and Davison charts need both birth times for their Ascendant, Midheaven and houses. Without them, the composite planets still work, since they come from the two sets of natal planets, but the composite Moon's degree is less certain and the houses and angles cannot be trusted. Synastry is more forgiving: its planet-to-planet contacts read from birth dates and places alone.

Can a good composite chart make up for difficult synastry?

A good composite chart and difficult synastry describe different layers of the same relationship. The composite can show a bond with a clear shared purpose, while synastry shows the specific frictions each person feels inside it. Astrologers read both rather than letting one cancel the other: the composite says what the relationship is for, and synastry says what each person has to work with.

Start with the two of you

The relationship is made of two people, so the clearest place to begin is how those two charts meet. Enter both birth dates and places on the compatibility page and you will see your strongest connections first, then the full reading of where you click, where you spark and what holds you together. If you have not read your own chart yet, start with your free birth chart.