Why sign tables are not enough
Popular compatibility begins with the question "What is your sign?" and ends with the sentence "You are a good match for Libra." The conversation is entertaining, but it says almost nothing about a particular couple: two people with a "perfect" Sun-sign combination may fail to understand each other for years, while an "incompatible" pair may build a durable union. The Sun sign describes a style of will and self-presentation. It does not describe the need for safety, the pace of intimacy, the way a person argues and repairs, attitudes to money, or the capacity to sustain obligation.
Synastry compares two natal charts by degree, not by sign. The planets, luminaries and angles of one person are set against the planets, luminaries, angles and houses of the other. The method does not answer "Is this a good couple?" It answers a different question: "What conditions appear when these two people are together?" A relationship has its own structure: points of attraction, recurring arguments, zones of ease and places where translation from one language to another is required.
The limits matter as much as the possibilities. Synastry does not measure love, predict a wedding date or a divorce, or cancel free will. A responsible reading ends not with a verdict but with a description of resources, risks and questions the couple may want to discuss.
Data first, interpretation second
Synastry begins with birth data, not aspects. The Moon moves about half a degree per hour; the Ascendant at middle latitudes shifts roughly one degree every four minutes; house cusps are sensitive to latitude and house system. If the birth time is unknown, a chart without houses and angles is still usable for inter-planet aspects, but overlays and Ascendant contacts cannot be built. Using a noon "solar" chart as if the time were known is a common and damaging practice.
Check the time zone and historical clock changes. A one-hour error can move the angles by about fifteen degrees, and the house cusps with them. Before reading, fix the conventions: tropical or sidereal zodiac (never mixed), one house system for both charts (quadrant, equal or whole sign), mean or true nodes, an orb table, and the direction of overlays.
Synastry is not the composite: the composite is a midpoint chart of the relationship, useful as a synthesis but not as a substitute for the aspect-by-aspect reading. An event chart describes the atmosphere of a moment, not the structure of a long relationship.
Inter-chart aspects: what is actually measured
An inter-chart aspect is the angular distance between a planet in one chart and a planet in the other, within the orb of a major aspect. Geometrically it is simple, but it is not a natal aspect. There is no applying or separating: both charts are static. There is no transfer of dignity: Venus in Taurus in one chart does not "strengthen" Mars in Virgo in the other. Each planet remains attached to its own person.
Three rules follow. First, do not use the language of transits — "almost exact", "already past", "active for two days". Second, do not count the same contact twice: "Sun A — Saturn B" and "Saturn B — Sun A" are one pair, although it can be described from both sides. Third, do not decide in advance that an aspect is good or bad. A square brings friction and energy; a trine brings ease and the risk of passivity; a conjunction blends functions and can be either support or confusion.
Five major aspects are enough for a basic reading: conjunction, opposition, square, trine and sextile. Minor aspects — quincunx, semisextile, semisquare — are added only after the main contacts and with narrow orbs. Otherwise the chart becomes noise in which every pair of planets "means something".
Orbs: fix the rule before you start
An orb is the tolerance within which an angular distance counts as an aspect. Synastry often uses wider orbs than a natal chart because two systems are interacting, but that is not permission to stretch the tolerance until a desired aspect appears. The main rule: fix the table before the reading and do not revise it when a beautiful hypothesis needs rescuing.
| Bodies | Conjunction and opposition | Square and trine | Sextile |
|---|---|---|---|
| Sun, Moon | 8–10° | 7–8° | 5–6° |
| Mercury, Venus, Mars | 6–8° | 5–7° | 4–5° |
| Jupiter, Saturn | 5–7° | 4–6° | 3–4° |
| Uranus, Neptune, Pluto | 4–6° | 3–5° | 2–3° |
| Angles | 3–5° | 3–4° | 2–3° |
This is a working frame, not a universal standard. Different practitioners use narrower or wider tolerances; the important thing is not to mix them in one reading. It helps to grade exactness: within one degree is the core, one to three degrees is strong, three to five is moderate, and near the edge is background. An exact aspect is not automatically more important than a wide one: a wide luminary contact may outweigh an exact minor aspect between outer planets. Exactness helps to rank contacts of the same type.
Choose one convention — an orb for the aspect or an orb for the planet — and apply it consistently; the rule must be single and explainable.
Weighting: how not to drown in aspects
Even with narrow orbs, a couple can produce several dozen contacts. If every contact receives equal attention, a random sextile of Uranus carries the same weight as an exact Sun–Saturn square. A second filter is needed: weighting. It combines the importance of the function (luminaries and angles above personal planets, personal above social, social above outer), the type of aspect (conjunction and opposition activate more strongly than trine and sextile), exactness, and repetition. A theme confirmed by an aspect, a house overlay and the composite weighs more than a single contact.
A simple teaching formula ranks contacts inside one couple: weight = planet coefficient × aspect coefficient × exactness coefficient.
| Factor | Value | Coefficient |
|---|---|---|
| Planet | Sun, Moon, angles | 3.0 |
| Mercury, Venus, Mars | 2.5 | |
| Jupiter, Saturn | 2.0 | |
| Uranus, Neptune, Pluto, nodes | 1.5 | |
| secondary points | 1.0 | |
| Aspect | Conjunction | 1.0 |
| Opposition, square | 0.9 | |
| Trine | 0.7 | |
| Sextile | 0.5 | |
| Minor | 0.2–0.3 | |
| Exactness | Within 1° | 1.0 |
| 1–3° | 0.8 | |
| 3–6° | 0.6 | |
| Near the orb edge | 0.4 |
An exact Sun A square Saturn B at 1.5° gives 3.0 × 0.9 × 0.8 = 2.16; Venus A conjunct Mars B at 4° gives 2.5 × 1.0 × 0.6 = 1.50. These numbers do not measure love; they help decide what to discuss first.
Use a "rule of three": a theme is stable when at least three independent indicators support it. A theme resting on one contact is a possible accent, not a law of the relationship.
The luminaries: the core of compatibility
The Sun and Moon describe the centre of the personality and the way safety is restored, so their contacts are read first.
Sun–Sun. A conjunction gives recognition — "we are alike" — a shared direction and a shared theme of self-expression, but also competition for attention. An opposition more often describes complementarity: one expresses what the other suppresses, together with the polarity "I am not like that". A square gives attraction and a struggle over pace and the right to lead; a trine or sextile gives easy recognition but not guaranteed closeness. Sun–Sun alone says neither marriage nor friendship: it is a contact of will.
Sun–Moon. A conjunction or opposition between the luminaries of different charts describes strong mutual completion: one person's will resonates with the other's emotional needs. It can be a marriage, a friendship or a working partnership; quality depends on the rest of the chart. A square gives attraction plus desynchronisation: one wants to act, the other wants to feel safe first. A trine or sextile eases the translation between "I do" and "I feel", but may create the illusion that difficult themes will resolve themselves.
Moon–Moon. Emotional rhythm, habits and ways of calming down. A conjunction gives similarity and mutual understanding, but also shared anxiety. An opposition is a polarity of closeness and space: one talks, the other goes quiet. A square means different recovery speeds after stress. A trine or sextile supports daily life, but without other contacts the relationship may remain comfortable and superficial.
Venus and Mars: affection and desire
Venus describes values, affection, the language of tenderness and money. Mars describes desire, initiative, sexuality and the way a person acts. Their contacts are read as "chemistry", but chemistry is not compatibility.
Venus–Venus. Similar tastes and ideas of beauty. A conjunction or trine gives the recognition "we like the same things"; a square brings different love languages and different attitudes to spending; an opposition attracts opposite aesthetics but requires negotiation.
Venus–Mars. The classic contact of desire. A conjunction combines tenderness and passion; an opposition attracts through polarity; a square brings passion with friction and a contest over initiative; a trine or sextile gives softer sensuality. Venus–Mars does not guarantee a long relationship: it describes how quickly desire ignites, not whether the couple can handle daily life, trust and conflict.
Mars–Mars. A similar reaction speed. A conjunction gives shared energy and competitiveness; a square brings competition, irritation and impulsive arguments; a trine gives coordination in action; an opposition attracts "strong" partners and a struggle over who goes first.
Venus–Saturn. Loyalty and a sense of duty, but the shadow is love experienced as obligation, or coldness in response to a need for tenderness. The contact is common in long unions, but duration is not happiness: ask what keeps the couple together — warmth or fear of loss.
Mars–Saturn. Discipline and endurance; under tension, suppressed anger and passive resistance. Mars–Jupiter adds scale, Mars–Uranus unpredictability, Mars–Pluto powerful will and a struggle for control.
Saturn: commitment or cage
Saturn describes structure, time, boundaries and fear. Its aspects often point to seriousness and duration, but the same planet can describe coldness, criticism and a relationship held together by duty.
Saturn–Sun. Respect and support, the feeling "I become more adult near you"; under tension, criticism and control. Saturn may be older in age or status, but not necessarily: the authority function can be carried by either partner. Saturn–Moon gives reliability but also emotional restraint: one person seems cold exactly when the other asks for warmth. In a mature form it is a durable family bond; in an immature form it is a relationship in which the need for tenderness feels shameful.
Saturn–Venus gives loyalty and serious intentions, but the shadow is love as obligation and fear of closeness. A useful question: if duty were removed, would interest remain? Saturn–Mars gives endurance and the ability to finish things, but under tension it brings suppressed anger and passive resistance.
Distinguish "stable" from "stuck". Saturn is often present in long relationships, but its presence does not prove that the relationship is good. Sometimes a couple stays together because of fear, children, money or status, and Saturn describes exactly that construction. The question is not "How long have we been together?" but "What holds us, and does it suit both of us?"
The lunar nodes: an axis of development
The lunar nodes are mathematical points where the Moon's orbit crosses the ecliptic, not physical bodies. They are always opposite: the North Node points toward development, the South Node toward the familiar comfort zone. In synastry the nodes are read as an axis of significance and growth, not as automatic proof of a "karmic" bond.
A planet on another person's North Node. A person feels that near the partner they become themselves, receive direction, learn. This can be inspiring, but it can also create dependence: "You are my compass." A planet on the South Node gives a sense of the familiar, "we have met somewhere before", ease and the repetition of old scenarios; it describes a resource, not a sentence.
Nodes to nodes. A conjunction of North Nodes gives a shared direction; an opposition brings opposite tasks; a square creates tension between the familiar and the new. Keep the language of growth rather than literal past-life stories.
Nodes in the partner's houses. A's North Node in B's seventh makes partnership a school of growth; in the tenth, a shared public goal; in the fourth, family and roots.
The nodes move slowly: a full cycle takes about 18.6 years, and the mean node travels about 19 degrees per year. A nodal contact therefore often links people of the same generation and does not by itself make a couple unique. Uniqueness appears when a node is precisely tied to a personal planet, an angle or a house.
House overlays: where the contact lands
Aspects show how functions meet; houses show the area of life in which the meeting is felt. A planet of A in a house of B activates that house for B. Overlays are counted by cusp, not by sign: a planet works in the house it occupies even when its sign differs from the cusp sign. Accurate birth time and one house system are therefore essential.
| B's house | A's planet activates | Resource | Shadow |
|---|---|---|---|
| 1 | Self-image, body, first impression | Vivid presence, recognition | Loss of self, dependence on approval |
| 2 | Money, resources, self-worth | Shared values, support | Arguments over money, possessiveness |
| 3 | Communication, learning, daily routine | Conversation, curiosity | Petty arguments, superficiality |
| 4 | Home, family, roots, foundation | A sense of the familiar | Family scripts, codependence |
| 5 | Romance, creativity, children, play | Inspiration, joy, flirtation | Drama, play without commitment |
| 6 | Work, health, routine, service | Shared effort, care | Criticism, unequal contribution |
| 7 | Partnership, marriage, open rivals | "My person" | Projection, struggle for equality |
| 8 | Intimacy, crisis, shared resources | Depth, trust, transformation | Jealousy, control, debt |
| 9 | Worldview, travel, education | Shared meaning, expansion | Dogmatism, clashes of values |
| 10 | Career, status, public role | Reputation support, shared goal | Competition, exploitation |
| 11 | Friends, communities, future | Friendship, shared plans | Jealousy of the circle |
| 12 | The hidden, the unconscious, solitude | Deep intuitive bond | Secrecy, idealisation, isolation |
Read overlays in both directions. If A's Sun falls in B's seventh house, B experiences A as a partner; what happens to A's seventh house is visible only in the second chart. This asymmetry often explains why one person experiences the connection as marriage and the other as an open relationship.
Step-by-step method
1. Verify date, time, place, time zone and the reliability of the birth time.
2. Read each chart separately: Sun, Moon, Ascendant, Venus, Mars, Saturn, nodes, dominant houses.
3. Fix the zodiac, house system, node type and orb table.
4. Build the cross-aspect grid and record distances.
5. Weight the contacts and keep the top ten to fifteen.
6. Start with the luminaries and angles.
7. Add Venus, Mars and Saturn.
8. Check the nodes and their links to personal planets.
9. Do the overlays in both directions; note angular houses and stelliums.
10. State three to five repeating themes.
11. Build the composite only as a synthesis, if needed.
12. Write resources, risks, questions and the limits of the method.
Example one: a long marriage
| Contact | Distance | Weight | What it describes |
|---|---|---|---|
| Sun A — Moon B | 2° opposition | 2.16 | Emotional recognition and complementarity |
| Moon A — Saturn B | 1° opposition | 2.16 | Tenderness meets restraint; durable duty |
| Mars A — Moon B | 2° conjunction | 2.00 | Drive and emotional reactivity |
| Saturn A — Venus B | 1° trine | 1.80 | Loyalty and a stable aesthetic bond |
Overlays: A's Moon in B's first house; A's Venus in B's tenth; A's Saturn in B's fourth; B's Moon in A's third; B's Venus in A's tenth; B's Saturn in A's fifth.
The chart shows a strong emotional bond with a serious tone. Sun–Moon brings recognition; Moon–Saturn adds reliability but also restraint; Mars–Moon gives liveliness and irritability; Saturn–Venus explains the durability of affection. The risk is not lack of love but emotional economy: one partner may experience duty where the other intended care. The public dimension is strong, while B's Saturn in A's fifth puts a brake on play. The useful question is not "Will it last?" but "What makes the endurance warm rather than merely long?"
Example two: a creative partnership
| Contact | Distance | Weight | What it describes |
|---|---|---|---|
| Sun A — Moon B | 3° conjunction | 3.00 | Shared direction and emotional buy-in |
| Moon A — Venus B | 3° sextile | 1.50 | Easy tenderness and aesthetic agreement |
| Venus A — Moon B | 3° sextile | 1.50 | The same ease in the other direction |
| Mars A — Venus B | 3° square | 1.80 | Creative friction and sexual charge |
Overlays: A's Sun and Mercury in B's seventh; A's Moon in B's fourth; A's Mars in B's fifth; B's Ascendant in A's seventh; B's Venus and Mars in A's eighth; B's Saturn in A's fourth.
The double Moon–Venus link gives mutual care, Sun–Moon a shared sense of purpose, and the Mars–Venus square supplies attraction and productive friction. The seventh-house emphasis makes the partnership itself the arena. The risk is to mistake creative chemistry for emotional readiness: the square is useful only when conflict is allowed to become material rather than resentment.
Common mistakes
Comparing signs instead of charts. The Sun sign is a style, not a relationship script.
Ignoring birth-time accuracy. Houses and angles without a reliable time are decoration; planet-only aspects are more honest.
Widening the orb to fit a hypothesis. A contact at 12° is not a working aspect, however useful it would be.
Treating Saturn as a guarantee of marriage. Saturn describes structure and time, not the quality of feeling.
Reading overlays in one direction only. Asymmetry is part of the picture.
Using synastry as pressure. "The stars say you must stay" is manipulation, especially dangerous where there is abuse or dependency.
Checklist before conclusions
- Birth data verified, including time reliability.
- Both natal charts read separately.
- Zodiac, house system and node type fixed.
- Orb table chosen in advance and unchanged.
- Contacts listed with distances and ranked.
- Luminaries and angles read first.
- Venus, Mars and Saturn read separately.
- Overlays checked in both directions.
- Themes stated through repetition.
- Limits of the method stated.
Timing and the limits of the method
Synastry describes the conditions of a relationship, not the date of an event. Timing comes from transits, progressions and directions set against the synastry or composite; even they give periods, not guaranteed events. Synastry therefore does not predict a wedding, a divorce or an affair — it shows where a theme may become active.
Conclusion
Synastry is a technique for comparing two charts, not a compatibility table. Its strength is discipline: verify the data, read the individuals, fix the orbs, weight the contacts, see the overlays, and only then assemble the themes. Its weakness is the temptation to find one aspect and explain the whole relationship with it.
Prepared by the [Astrobot](https://astrobot.chat) team. Based on the classical and modern astrological tradition.
endant, Moon, houses and aspects, monthly theme synthesis, timing by lunar houses and phases, comparison with natal and solar returns, limitations and common mistakes.