Synastry is a technique in astrology used to analyze the relationship between two people by comparing their birth charts.
A synastry chart overlays two natal charts to examine how planets interact between partners.
Today, synastry analysis is usually done using astrology software or a synastry chart calculator.
Astrologers use synastry to understand:
- romantic compatibility
- emotional dynamics
- communication styles
- relationship challenges
A synastry chart compares the planetary placements of two individuals.
Astrology chart software automatically calculates these aspects and displays them in an easy-to-read format.
Key comparisons include:
- planet-to-planet aspects
- planets in partner's houses
- Sun-Moon compatibility
- Venus-Mars attraction
For example:
- Moon-Moon aspects reveal emotional compatibility
- Venus-Mars aspects show romantic attraction
- Mercury aspects influence communication
Some aspects are considered especially significant in relationships.
Conjunction
Two planets occupy the same position in the zodiac.
This creates strong interaction between the energies.
Trine
Planets are 120 degrees apart, creating harmony and ease.
Square
Planets are 90 degrees apart, which can create tension or growth opportunities.
Opposition
Planets are 180 degrees apart and often represent polarity in relationships.
Many astrology tools also include composite charts.
Both techniques are widely used in professional astrology practice.
Synastry chart:
compares two charts directly
Composite chart:
creates a new chart representing the relationship itself
Calculating synastry manually involves comparing dozens of planetary relationships across two charts.
This allows astrologers to analyze relationship dynamics quickly and accurately.
Modern astrology software simplifies this by:
- automatically generating comparison charts
- highlighting major aspects
- calculating orb differences
- visualizing the interaction between charts
The software then generates a compatibility chart showing planetary interactions.
Many astrologers consider synastry one of the most powerful techniques for understanding relationships.
A synastry calculator requires:
- person A birth date, time, and location
- person B birth date, time, and location