Synastry is the astrology of relationships: the technique of comparing two birth charts to understand the dynamic between two people. Open a synastry chart and you’ll see two wheels overlaid, dozens of inter-chart aspects, and enough lines to look like a flight map. It’s overwhelming — until you know what to look at first.
This guide gives beginners a prioritized reading order: the five layers that matter most, in the sequence a professional would actually check them. Follow it and you can read any synastry chart with confidence.
What Synastry Is (and Isn’t)
Synastry places two natal charts in the same wheel and reads the aspects between one person’s planets and the other’s — your Venus to their Mars, your Moon to their Sun, and so on. It describes the chemistry and dynamics between two people: what flows, what frictions, what fascinates.
What synastry isn’t: a score, a verdict, or a prediction about whether a relationship will “work.” Two charts describe potentials and patterns, not outcomes. The same synastry can describe a transformative partnership or a dramatic collision — the difference is the people, not the planets. Hold that before you read a single aspect.
(A related technique, composite charts — blending two charts into one “relationship chart” — describes the relationship itself as an entity. Synastry first; composite later, once you’re comfortable.)
Layer 1: The Moons — Emotional Attunement
Start here, always. Compare the two Moon signs: same element is the easiest attunement; challenging combinations need translation. Then check Moon-to-Moon aspects and each Moon’s aspects to the other’s personal planets.
Why first? Because the Moon governs daily emotional life — comfort, safety, instinctive reactions. A couple with harmonized Moons can weather almost anything; a couple with clashing Moons will feel the friction every single day, in small moments. Our deep dive into Moon sign compatibility covers this layer fully.
Key contacts to note: Moon conjunct or trine the other’s Moon, Sun, or Venus (emotional warmth and mutual care); Moon square or opposite the other’s Moon or Mercury (emotional misattunement — workable, but name it).
Layer 2: Venus and Mars — Affection and Desire
Next, the romantic wiring. Compare Venus signs (affection style, values — do you love in mutually intelligible ways?) and Mars signs (desire, pursuit, conflict style). Then look for the cross-contacts:
- Venus-Mars contacts between charts (your Venus to their Mars or vice versa): the classic chemistry signature. Conjunctions and trines describe strong mutual attraction.
- Venus-Venus harmony: shared love language; you appreciate the same things.
- Mars-Mars contacts: how your drives interact — mutual motivation or power friction.
- Venus-Saturn contacts: seriousness and staying power in the bond — or reserve that needs warming.
This layer answers: is there spark, and do we like in compatible ways? Chemistry without attunement (Layer 1) burns bright and short; attunement without chemistry can feel like deep friendship. You want both — and now you know where to look for each.
Layer 3: Sun and Mercury — Identity and Communication
Compare the Sun signs for core-orientation harmony (the familiar Sun-sign compatibility — real, but just one layer). More importantly, check Sun-to-personal-planet aspects between charts: your Sun conjunct their Moon or Venus often describes a feeling of being deeply “seen”; Sun square their Mars can describe ego friction.
Then Mercury: can these two people actually talk? Mercury-Mercury harmony (same element, trine, sextile) describes easy conversation; Mercury square Mercury describes talking past each other — different mental wavelengths. In long relationships, Mercury compatibility is criminally underrated: most couples spend more hours talking than doing anything else together.
Layer 4: Saturn — The Container
Saturn contacts between charts are the most misunderstood layer in synastry. Saturn-to-personal-planet aspects (your Saturn to their Sun, Moon, Venus…) describe commitment, responsibility, and staying power — the container that holds the relationship through hard seasons.
They can also feel heavy: Saturn on someone’s Venus can feel like love with conditions; Saturn on the Moon can feel emotionally reserved. The mature reading: Saturn contacts describe where the relationship asks for work and patience — and relationships with strong Saturn contacts are often the ones that last, precisely because they’ve been built deliberately.
Don’t fear Saturn in synastry. Fear its absence: all spark and no Saturn can describe connections that never quite become committed.
Layer 5: The Angles and Outer Planets — Refinement
Finally, the refinements:
- One person’s planets on the other’s angles (Ascendant, Descendant, Midheaven): powerful. Your planets on their Descendant (7th-house cusp) often describes strong partnership significance — you “embody” what they seek in a partner.
- Outer-planet contacts (Uranus, Neptune, Pluto) to personal planets: generational planets move slowly, so these describe era-flavored dynamics — intensity, idealization, or disruption themes. Significant when tight, but weight them below personal-planet contacts.
- House overlays (your planets falling in their houses): describes where you activate their life — your Venus in their 7th house emphasizes partnership; your Mars in their 10th activates their ambition. A rich layer once the basics are covered.
How to Read a Synastry Chart in Practice
- Get both birth times if you can. Houses and angles need times; without them, stick to planet-in-sign and inter-aspects (still substantial).
- Work the layers in order: Moons → Venus/Mars → Sun/Mercury → Saturn → refinements. Don’t cherry-pick one dramatic aspect.
- Sort aspects by orb. Tight (under 3°) contacts dominate; wide ones are background.
- Count themes, not aspects. Three separate contacts all pointing to “emotional intensity” is one theme, stated three ways. Themes are the reading; aspects are the evidence.
- End with a synthesis paragraph, not a score: “This connection centers on [theme], supported by [harmony], with [friction] as the growth edge.”
The Bottom Line
Synastry for beginners is a prioritized checklist: Moons first (daily attunement), Venus and Mars (romance and desire), Sun and Mercury (identity and communication), Saturn (the container), then angles and outer planets as refinement. Work the layers in order, sort by orb, synthesize themes — and never let a single aspect, however dramatic, override the whole picture.
Put it into practice: compare your full compatibility across all the key layers, with both birth charts calculated first. For the tarot perspective on a connection, try our relationship spread.