Astrology guide
What is synastry in astrology?
Two charts in conversation, not a relationship verdict.
- By
- Astral Meridian
- Published
Short answer
Synastry is the astrological comparison of two birth charts. It looks at contacts between one person's planets and the other's planets or angles, and sometimes house overlays. It is more detailed than matching Sun signs, but it cannot prove compatibility, consent, or a relationship outcome. Time-sensitive comparisons need reliable birth data for both people.
What a two-chart comparison does
A synastry comparison keeps both natal charts. It checks interchart aspects: angles between a placement in one chart and a placement in the other. For example, one person's Mercury might be close to the other's Moon by zodiac degree.
Astrologers attach symbolic meanings to those contacts. They may use them as prompts for discussing different habits or preferences. The measured angle is a chart fact; a claim about how two people relate is interpretation.
Why Sun-sign matching is only a small part
Comparing two Sun signs uses one factor from each chart. Synastry may also consider the Moon, Mercury, Venus, Mars, and other placements. A whole-chart comparison should not be reduced to one supposedly perfect or impossible sign pair.
A close contact can support more than one reading. An easy aspect does not prove respect or shared values. A tense aspect does not prove conflict or an unsafe relationship. Those judgments need real behaviour and context.
Birth-time limits and house overlays
A house overlay places one person's planet within the other person's house layout. It depends on the receiving chart's reliable birth time and the stated house system. Contacts to either person's Ascendant or MC need reliable time and place for that angle.
Unknown birth time also makes exact Moon contacts less certain and can leave its sign unresolved on a sign-change date. Compare only placements supported by the data. Do not turn a placeholder-time chart into a precise relationship reading.
Synastry is different from a composite chart
Synastry compares two separate charts. A midpoint composite combines the mathematical midpoints of corresponding placements into a new chart. It is a different technique, not another name for the same comparison.
Neither method measures the quality of a real relationship. This guide explains the terminology; it does not promise a dedicated synastry or composite-chart calculator in Astral Meridian.
Keep consent and real behaviour first
Ask before using or sharing another person's birth details. A chart comparison is not permission to publish their private information or make claims about their feelings.
Use the reading as an optional conversation prompt, not a reason to stay, leave, pursue someone, or disregard a boundary. Consent, communication, and observed behaviour matter independently of any chart contact.
What this can and cannot say
Synastry is symbolic comparison, not a validated compatibility test or a prediction of attraction, commitment, or separation. Missing birth times limit Moon details, angles, and house overlays. No chart establishes another person's feelings or replaces consent, boundaries, and real communication.
One Mercury–Moon contact
Suppose one person's Mercury is close to the other's Moon by degree, using reliable data and a stated orb. A reader might use this as a prompt to discuss how words and familiar responses meet. It does not prove mutual understanding, attraction, or a lasting bond.
Sources and method
Linked sources support the factual claims identified in each section. They do not establish or validate the symbolic interpretations, which are presented as reflection.
- Cafe Astrology: synastry and interchart contacts
Supports: synastry terminology and the comparison of planets and points across two natal charts.
- Cafe Astrology: synastry versus composite charts
Supports: the distinction between comparing individual charts and reading a separate relationship chart.
- Cafe Astrology: composite chart construction
Supports: the midpoint construction of a composite chart, not claims about relationship viability.
Frequently asked questions
- Can synastry tell me if someone is right for me?
- No. It can provide symbolic prompts for a conversation, but it cannot assess consent, respect, shared values, or a relationship's future.
- Can synastry be read without birth times?
- Some reliable planetary contacts can be compared. Leave uncertain Moon contacts, angles, and time-dependent house overlays out rather than guessing them.
- Is synastry the same as a composite chart?
- No. Synastry compares two natal charts. A midpoint composite creates a separate chart from midpoints between corresponding placements.