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Relationship astrology

What is synastry? How two birth charts are compared

Synastry compares two natal charts through cross-chart aspects and house overlays; it describes relationship dynamics, not compatibility as a single score.Reviewed · 2026-08-24 · Educational astrology content
Direct answer

Synastry places one person’s planets in relation to another person’s chart. Cross-chart aspects can describe attraction, ease, friction, communication, and timing sensitivities, while house overlays show where one person’s placements activate the other chart.

Key points

  • Both natal charts must be interpreted before comparison.
  • Exact birth times are needed for reliable house overlays.
  • One difficult aspect does not define a relationship.
  • Consent and real behavior matter more than symbolic compatibility.

Method

  1. Validate both birth datasets.
  2. Start with Moon, Mercury, Venus, Mars, Saturn, and angles.
  3. Look for repeated themes and reciprocal contacts.

Limits and responsible use

  • Synastry cannot prove that a relationship will begin, last, or be safe.
  • Do not use it to excuse coercion or harmful behavior.