The three layers we read
We read two charts against each other in three layers.
Cross-aspects: how the planets meet
An aspect is an angle between two points in the zodiac: together in a conjunction, facing each other in an opposition, a third of the circle apart in a trine, a quarter in a square, a sixth in a sextile. Our guide to aspects explains what each one tends to mean inside a single chart. In synastry the aspects run between the charts: your Venus to the other person's Moon, their Saturn to your Sun.
That is a great many pairs. With the orbs used inside one chart, nearly every planet would touch something in the other, and the reading would blur. So between two charts we use tighter orbs, measured as the distance from the exact angle:
| Aspect between the two charts | Orb | With either person's Sun or Moon | With either person's Ascendant or Midheaven |
|---|---|---|---|
| Conjunction | 6° | 7½° | 3° |
| Opposition | 6° | 7½° | 3° |
| Trine | 5¼° | 6¾° | 3° |
| Square | 5¼° | 6¾° | 3° |
| Sextile | 3¾° | 5¼° | 3° |
When either person's Sun or Moon takes part, the orb widens: the two lights are the centre of a chart, and tradition gives them more room. A trine to the Moon counts up to 6¾° from exact; the same trine between Venus and Mars, up to 5¼°. When either person's Ascendant or Midheaven takes part, the orb narrows to 3°. These points turn with the Earth's daily rotation and depend on the birth time to the minute, so only a close contact can be trusted. Within the orb, the nearer an aspect is to exact, the more weight we give it.
House overlays: where one person lands in the other's life
A chart has twelve houses, the areas of life in which a planet acts. In synastry we place one person's planets in the other person's houses. If your Moon falls in your partner's fourth house, the house of home and roots, astrologers read it as a sense that you bring comfort into their private life. Your Mercury in their ninth house tends to show as conversations that widen their view of the world. Overlays run both ways, and the two directions often tell different stories.
Houses depend on the exact time and place of birth. To place your planets in your partner's houses, we need your partner's birth time and birthplace; to place theirs in yours, we need yours.
Sun and Moon elements: kindred, complementary, contrasting
The simplest layer compares the elements of the two Suns, then of the two Moons, and names the relation:
- Kindred: the same element. Two fire Suns, or two water Moons, start out speaking the same language.
- Complementary: fire with air, or earth with water. These elements feed each other: air lets fire burn, and earth gives water a shape to hold.
- Contrasting: every other pairing, such as fire with water or air with earth. The two people come at things from different directions, and each has something the other lacks.
These are descriptions, not verdicts. Kindred elements often bring quick understanding, and sometimes shared blind spots. Contrasting Moons, say one in Aries and one in Cancer, handle a feeling differently: the fire Moon wants to act on it at once, the water Moon needs to feel it all the way through. On a bad evening that causes friction; on another, each gets from the other what they could not supply themselves. Our guide to elements and modalities goes further into the four elements.
The contacts astrologers look at first
Astrologers usually start with the contacts below. In each, the type of aspect sets the tone: a conjunction fuses the two planets, a trine or sextile lets them flow into each other, and a square or opposition sets them working against each other, which brings friction and also movement.
Sun–Moon
One person's Sun in aspect to the other's Moon is the classic contact of synastry. The Sun person's sense of purpose meets the Moon person's emotional needs. In a conjunction or trine, the Moon person often feels recognised, and the Sun person feels supported in what they are building. In a square, the Sun's plans can press on the Moon's need for comfort, and both have to give a little.
Moon–Moon
The two Moons describe emotional rhythm: what each person needs after a long day, how each reacts to a quarrel. When the Moons are conjunct or share an element, everyday life together tends to feel natural. When they square, one person may want to talk a disagreement through at once while the other needs an evening alone first, and each has to learn the other's timing.
Venus–Mars
Venus describes what a person finds attractive and how they show affection; Mars, how they go after what they want. Venus–Mars contacts across two charts are the best-known signature of attraction. In love they often describe the spark. In friendship the same contact tends to show as energy for shared projects, or a playful rivalry.
Mercury contacts
Mercury describes how each person thinks and talks. A trine from one Mercury to the other person's Mercury or Moon tends to make conversation easy. A square can bring lively disagreement: two minds that sharpen each other on a good day and talk past each other on a tired one.
Contacts to the Ascendant
The Ascendant, or rising sign, describes a person's manner. When one person's planet sits on or aspects the other's Ascendant, that planet tends to colour first impressions: someone's Venus on your Ascendant is often read as finding your manner attractive from the start. These contacts need the birth time and place of the person whose Ascendant it is.
Saturn contacts
Saturn stands for structure, responsibility and limits. Saturn contacts across two charts bring weight: loyalty, seriousness, a sense of duty. Many astrologers count them among the ties that hold long commitments together, and among the sources of their heaviest moments. The Saturn person can feel like a steadying hand or like a critic.
The same aspect in love and in friendship
Mars opposite Venus between two lovers may read as magnetism; between two colleagues, as competition. Saturn on the Moon can feel like dependable care in a long friendship, and like being corrected in a new romance. We therefore read a pair of charts for a particular relationship, never in the abstract.
Holding two contacts together: an example
Take two invented people, A and B. A's Venus is in Cancer and B's Moon is in Scorpio: a trine between two water signs. A's Mars is in Aries and B's Saturn is in Capricorn: a square between two cardinal signs.
On its own, the Venus–Moon trine says that A's affection arrives in a form B's emotional needs recognise. Venus in Cancer loves by caring and protecting; the Moon in Scorpio needs depth and tested trust before it feels safe. A's steady, attentive care is the kind of proof B is looking for.
The Mars–Saturn square says something else. A's drive is quick and direct, as Mars in its own sign tends to be. B's Saturn in Capricorn is deliberate and slow to commit. When A pushes to act, B tends to brake. A may feel held back; B may feel rushed.
Listed separately, the two contacts seem to contradict each other: one calls the connection easy, the other hard. Read together, they give a truer picture. The trine gives both people a reason to stay with the friction, and the square keeps the warmth from settling into routine; it asks patience of A, and asks B to trust a quicker pace now and then. In a romance the square might show as recurring arguments about timing. In a friendship it might show as one person who always proposes the plan and another who always checks it, a pairing that tends to get things finished.
Why we give no compatibility score
Many apps and websites turn synastry into a score: points added for trines, points taken away for squares. We do not, because a relationship is not a number. A score treats tension as a defect and ease as a gift, and relationships rarely work that way. Tension can keep two people interested in each other for a long time. Ease can turn into inertia, two people so comfortable that nothing moves them.
A chart also describes tendencies, not choices. Two couples with near-identical synastry can build very different relationships, because they bring their own histories and make their own decisions. So we describe where things come easily and where the work lies, and leave the judging to the two people. No score, rating or verdict appears anywhere in what we write about a pair.
When birth data is missing
Without a birth time, a chart is cast for noon local time. Most planets change little in a day, but the Moon moves about 13° a day, 13.2° on average. A noon Moon can be up to half a day's motion from where it really stood, about 6.6° on an average day, close to the widest Moon orb in the table, 7½°. An aspect to that Moon could be real or an artefact of the guess, so we leave that person's Moon out of the cross-aspects. Its sign can still be read if the Moon stayed in one sign all day; if it changed sign that day, both signs are named.
Without a birth time, or without a birthplace, a chart has no houses, Ascendant or Midheaven. Nobody's planets can then be placed in that person's houses, and there are no contacts to their angles. Their planets can still fall in the other person's houses, as long as the other person's time and place are known. Our guides to a chart without a birth time and to finding your birth time go further. Natalore's two-person reading asks only a first name and birth data of the second person, and nothing more.