Astrology Journal
Birth Chart Compatibility: How Synastry Really Works
There is a particular thrill to laying two birth charts side by side. Birth chart compatibility, known to astrologers as synastry, is the art of comparing two people's charts to see how they meet, where they flow, and where they will gently challenge each other. It is the most romantic corner of astrology, and one of the most genuinely useful.
What synastry is
A synastry chart takes your birth chart and your person's birth chart and overlays them, so you can see the conversation between the two skies you were each born under. Where your planets touch theirs, a connection is made. Your moon meeting their sun, your Venus meeting their Mars, your Saturn brushing their moon: each of these contacts has a flavour, and together they describe the weather of your relationship.
Crucially, synastry is not a verdict. No chart comparison decides whether two people belong together. What it offers is understanding: a map of where things will feel effortless and where they will ask for patience, so you can love each other with your eyes open.
The aspects that matter most
In compatibility, the angles between your planets are everything. A few to know:
- Conjunction: two planets in the same place, fused and intense. A powerful meeting that can feel like recognition.
- Trine and sextile: the easy, flowing contacts. These are where you understand each other without trying, the natural grace of a relationship.
- Square: a productive friction. You want different things here, and learning to honour both, rather than silencing one, is where couples grow.
- Opposition: a magnetic pull between opposites, equal parts attraction and tension, forever asking you to find the balance.
The planets involved colour the story. Sun and moon contacts speak of deep compatibility and feeling at home together. Venus and Mars contacts bring chemistry and desire. Saturn contacts ask for commitment and maturity. Mercury contacts decide whether you simply love talking to each other.
See how your charts connect. Enter both birth details and Astralune reveals your compatibility: a clear score, every connection between you, and a free written guide in plain English.
Reveal your compatibility, freeWhy compatibility readings are the loveliest gift
A synastry reading is a quietly intimate thing to share with someone. It says, I am curious about us, I want to understand you. Whether you are newly falling or years deep, seeing your two charts together can name the things you already feel and soften the things you have argued about. The friction stops feeling personal and starts feeling like weather you can learn to dress for.
If you are new to all this, it helps to know your own chart first. Start with your Big Three, then bring your person in and see what the two skies have to say to each other.