When people think about astrology and relationships, they often start with sun sign compatibility, like, “I’m a Taurus, and they’re a Scorpio—will we get along?” While this is a good first step, astrology can actually tell us a lot more about relationships. Synastry, which involves comparing two people’s birth charts, gives a deeper and more detailed look at how two individuals connect and interact with each other.

The Limitations of Sun Sign Compatibility

Your sun sign represents your core identity and ego—an essential part of who you are, certainly. But it’s just one piece of your astrological makeup. Think of your birth chart as a complex symphony with many instruments playing simultaneously; your sun sign is merely the lead violin. When we reduce relationship compatibility to sun signs alone, we’re essentially judging an entire orchestra by a single instrument.

For example, a Gemini and Sagittarius sun sign pairing is traditionally considered compatible—both are curious, adventurous, and value intellectual stimulation. Yet many Gemini-Sagittarius couples struggle with commitment issues or feeling emotionally disconnected. Why? Because their moon signs, Venus placements, and other crucial chart factors might tell a completely different story.

What Is Synastry?

Synastry is a specialized branch of astrology that examines the relationship between two individuals by comparing their natal charts. Unlike basic sun sign compatibility, synastry analyzes how all the planets and points in one person’s chart interact with all the planets and points in another person’s chart.

When an astrologer conducts a synastry reading, they overlay two birth charts and examine:

• The aspects (angular relationships) formed between planets across both charts
• Where one person’s planets fall in the other person’s houses
• The overall balance of elements and modalities between charts
• The condition of each person’s relationship-oriented planets (Venus, Mars, Moon)
• Special points of connection like the Vertex, Nodes, and Juno

Each of these factors contributes to a comprehensive understanding of relationship dynamics that simply cannot be captured by sun sign compatibility alone.