Reading two charts together
Synastry is the astrological method of laying the natal chart of one person over that of another to see how the two interact. Instead of asking what a person is like, it asks what happens between two people. Astrologers look at the angles, called aspects, between the planets of one chart and the planets of the other, and at where the planets of each person fall in the houses of the other.
Synastry is used for romance, but it applies equally to friendships, family, business partners and teachers. Because each person brings a whole natal chart, a synastry reading always starts with knowing each chart on its own.
What you need
Each person needs a date, an exact time and a place of birth. The planets in signs can be compared with only a date, but the contacts to the Ascendant and the house overlays need a time. If one time is unknown, use the planet contacts only and treat the house overlays with caution.
Key contacts
Astrologers pay most attention to a few contacts, and they weigh the closest ones, within about three degrees, most heavily.
Sun and Moon. The Sun of one person in a smooth aspect with the Moon of the other is a classic sign of comfort. One feels understood and the other feels appreciated. A harder aspect can feel like a push and pull between need and identity.
Moon and Moon. Shows how well the emotional rhythms match. The same Moon element often means similar habits and a shared sense of home. See the page on the Moon sign.
Venus and Mars. The classic contact for attraction. Venus of one person and Mars of the other, linked by a conjunction, trine, sextile or even opposition, often bring a strong pull and a sense of chemistry.
Venus and Venus. Shows shared taste, affection and values. A trine or sextile tends to bring ease, while a square shows different ways of giving love.
Mercury and Mercury. Shows how well two people talk and think. A good link makes conversation easy.
Saturn contacts. Saturn touching a personal planet in the other chart often brings commitment, duty and also restriction. Many long marriages show Saturn contacts, which can feel heavy at first and stable in time.
Ascendant and Descendant. The Sun, Moon or Venus of one person conjunct the Ascendant of the other often creates a feeling of instant recognition. The rising sign shows first impressions, so these contacts shape how two people see each other from the start.
Nodes. Contacts to the lunar nodes are called karmic by many astrologers and are said to give a sense of fate or meeting for a reason. Treat this as a poetic idea and not as proof.
House overlays
When the planets of one person fall in the houses of the other, they act in those areas of life. Venus of one person in the seventh house of the other suggests romance or partnership. The Moon in the fourth house suggests a sense of home. Saturn in the first house can feel like being judged or guided. See the 12 houses for the meaning of each area.
Composite and Davison charts
A composite chart combines two charts into one, by taking the midpoint of each pair of planets, and describes the relationship as an entity of its own. A Davison chart is built from the midpoint in time and space between the two birth moments. Astrologers use these to see the purpose and style of a relationship, while synastry shows how each person affects the other.
How to read a synastry chart
- Study each natal chart alone before comparing them.
- List the tight contacts between personal planets, meaning the Sun, Moon, Mercury, Venus and Mars, and between those and Saturn.
- Mark how many contacts are easy and how many are hard. A mix is normal, and a chart with no tension at all often feels flat.
- Look at the house overlays to see which areas of life each person activates in the other.
- Check the composite chart if you want to see the style of the relationship as a whole.
- Keep the result in proportion. Many other factors matter more, such as kindness, honesty and shared goals.
What synastry cannot do
Synastry cannot say whether a relationship will last. Couples with difficult charts build good relationships, and couples with easy charts separate. The reading shows tendencies, such as where communication is easy and where friction is likely, and it can help two people understand each other. It should never replace talking, nor be used to decide a major life choice alone. Scientific studies have not found that chart compatibility predicts relationship outcomes, so treat the comparison as a thoughtful conversation starter.