Synastry — Chart Comparison (合盤——命盤比較)
Synastry is the technique of comparing two natal charts to assess the dynamics of a relationship — romantic, familial, professional, or otherwise. One person's planetary positions are overlaid onto the other person's chart, and the resulting inter-chart aspects reveal how the two people activate, challenge, or support each other.
Core Synastry Method
The primary synastry technique places Person A's planets in the houses of Person B's chart (and vice versa), then identifies all inter-chart aspects:
- Conjunctions: The most powerful synastry aspect. One person's planet sits directly on another's — intense merging of those two themes. Sun conjunct Moon across charts: the Moon person feels seen and nurtured by the Sun person; the Sun person feels creatively inspired by the Moon person.
- Trines and Sextiles: Easy, supportive flows between the two charts. Natural compatibility in those planetary themes.
- Squares: Friction and challenge between the two charts. Not incompatibility, but the energy that creates growth through tension. Many long-term couples have significant square aspects.
- Oppositions: Attraction through polarity — each person embodies what the other lacks. Fascinating, sometimes destabilising.
The Most Significant Synastry Contacts
- Luminaries to Angles: One person's Sun or Moon conjunct the other's Ascendant, Descendant, IC, or MC. These are the most powerful relationship signatures, indicating a profound impact on each other's core life narrative.
- Venus-Mars contacts: The classic romantic attraction signature. Venus conjunct or trine Mars across charts indicates strong physical and romantic chemistry.
- Saturn contacts: Saturn to the other's personal planets (Sun, Moon, Venus) indicates a serious, committed, karmic relationship — often with one person playing teacher/restrictor to the other. Common in long marriages.
- Moon-Moon contacts: Emotional resonance (trine/sextile) or emotional friction (square/opposition). Determines how comfortable the two people feel in each other's daily presence.
- Nodal contacts: One person's planets conjunct the other's North or South Node. These indicate karmic connections — relationships that feel fated, linked to past life patterns, or carrying a sense of destiny.
House Overlays
When Person A's planets fall in Person B's houses, they activate those life areas for Person B. Person A's Venus in Person B's 4th house: Person A brings love, beauty, and harmony into Person B's home and family life. Person A's Saturn in Person B's 7th house: the relationship may feel restrictive or serious in the partnership domain.
Vedic Parallel — Kundali Milan (குண்டலி மிலான்)
Vedic astrology uses an elaborate matching system called Ashtakuta (eight-fold compatibility) for marriage assessment. Points (Gunas, up to 36) are assigned across eight categories including Moon sign compatibility (Rashi), star compatibility (Nakshatram), temperament (Gana), and generational compatibility (Gotra). The emphasis on Moon-sign matching in Vedic practice mirrors the Western synastry emphasis on Moon contacts as the primary indicator of emotional compatibility.