In your own birth chart, aspects describe how your own planets interact with each other. In synastry, aspects describe how your planets interact with another person's planets. These cross-chart aspects are the engine of a relationship — they reveal where energies merge, flow, clash, and transform.
What Makes a Cross-Chart Aspect
A synastry aspect forms when a planet in Person A's chart is within a certain angular distance — called the orb — of a planet in Person B's chart. The smaller the orb, the tighter the aspect, and the stronger its influence.
The six major aspects in synastry:
| Aspect | Angle | Orb | Quality | |---|---|---|---| | Conjunction | 0° | ±8° | Intense merger of energies | | Sextile | 60° | ±6° | Cooperative, supportive | | Square | 90° | ±8° | Dynamic tension, growth | | Trine | 120° | ±8° | Natural flow, ease | | Opposition | 180° | ±8° | Magnetic contrast, balance | | Quincunx | 150° | ±3° | Adjustment, integration |
In synastry, most astrologers work with slightly tighter orbs than in natal charts — within 6–8° for major aspects. Aspects under 3° are considered very strong.
The Most Important Aspect Combinations
Sun–Moon Aspects (The Compatibility Classic)
This is the most discussed synastry aspect for good reason. When one person's Sun connects with another's Moon, there's a sense of fundamental recognition — the Sun person feels lit up by the Moon person, and the Moon person feels emotionally nourished by the Sun person.
Sun conjunct Moon — The most powerful Sun-Moon connection. The Sun person's core identity and the Moon person's emotional nature feel deeply aligned. Often described as a "soulmate" signature, though it can also mean intensity and occasional over-enmeshment.
Sun trine Moon — Easy, flowing compatibility. The relationship feels natural, comfortable, and supportive without requiring much effort. Both people feel seen and accepted.
Sun square Moon — Productive friction. The Sun person's sense of self can sometimes clash with the Moon person's emotional needs. But this tension often creates growth and keeps the relationship dynamic. Not a dealbreaker — many lasting relationships have this.
Sun opposition Moon — A push-pull of complementary energies. The Sun person's identity pulls in one direction while the Moon person's emotions pull in another. Can feel like completion through contrast — each person has what the other needs.
Venus–Mars Aspects (Attraction and Desire)
Venus-Mars aspects are the classic attraction signature in synastry. Venus represents what we find beautiful and what we offer in love; Mars represents desire and what we pursue. When they connect across two charts, chemistry follows.
Venus conjunct Mars — Raw attraction. The Venus person feels adored by the Mars person's pursuit; the Mars person finds the Venus person irresistible. High physical and romantic chemistry.
Venus trine Mars — Attraction with ease. The chemistry is real but not overwhelming. The relationship flows naturally between romantic gesture and emotional warmth.
Venus square Mars — Passionate friction. The attraction is intense but so is the potential for conflict around desire and values. This aspect often appears in relationships with high passion and high drama.
Venus opposition Mars — Strong attraction through contrast. The Venus person's softness and the Mars person's drive pull toward each other magneticall. The challenge is negotiating very different approaches to love and desire.
Moon–Moon Aspects (Emotional Attunement)
The Moon governs your emotional instincts, how you self-soothe, what you need to feel safe. Two people's Moons in harmony means emotional life feels natural together — you don't have to explain your moods.
Moon conjunct Moon — Deeply similar emotional natures. You react to the world in similar ways, need similar things for comfort, and intuitively understand each other's inner states. Can be supportive or occasionally suffocating.
Moon trine Moon — Comfortable emotional compatibility. Different emotional styles that complement rather than clash. Natural empathy flows in both directions.
Moon square Moon — Emotional friction. Your instinctive reactions often don't match. One person's need for space conflicts with the other's need for closeness, or your security needs differ fundamentally. Requires conscious communication.
Saturn Aspects (Commitment and Longevity)
Saturn aspects in synastry are often misunderstood. They can feel heavy — Saturn introduces obligation, discipline, and reality-testing into a relationship. But they are also the glue that makes relationships last.
Saturn conjunct/trine personal planets — The Saturn person brings structure, reliability, and grounding to the planet person. The planet person often feels supported and stabilised. The relationship tends toward commitment and durability.
Saturn square/opposition personal planets — The Saturn person can feel restrictive, critical, or demanding to the planet person. The planet person may feel held back. But this friction, if worked through consciously, creates real growth. Many of the most important relationships in people's lives have Saturn squares.
A Saturn connection often means the relationship is significant — not necessarily easy, but lasting and formative.
Pluto Aspects (Intensity and Transformation)
Pluto aspects in synastry describe relationships that change you. Not always comfortably.
Pluto conjunct personal planets — Intensely transformative. The Pluto person tends to see through the planet person, drawing out deep psychological material. These relationships feel fated, powerful, and sometimes obsessive. They fundamentally change who you are.
Pluto trine/sextile personal planets — Transformation with less turbulence. The Pluto person catalyses growth and depth in the planet person's area of life without the volatility of harder aspects.
Pluto square/opposition personal planets — Power dynamics are likely. The potential for control, obsession, or profound transformation is high. These aspects appear frequently in relationships that are deeply significant but also deeply challenging.
Hard Aspects vs. Soft Aspects — Neither Is Bad
A common misconception: trines and sextiles are "good" and squares and oppositions are "bad." In practice, this isn't accurate.
Soft aspects (trine, sextile) bring ease — but sometimes so much ease that there's no growth and the relationship becomes stagnant. Couples with only soft aspects may find they lack the friction that creates depth.
Hard aspects (square, opposition) bring tension — but tension creates engagement, growth, and chemistry. Many people report that their most important relationships have significant hard aspects. The key is whether both people are mature enough to work with the friction rather than be destroyed by it.
The best synastry charts typically have a mix: enough ease to feel supported, enough tension to fuel growth.
Orbs: Tighter Means Stronger
In synastry, aspect strength scales with orb tightness. A Venus conjunct Mars within 1° is electric — you'll feel it the moment you meet. The same aspect at 7° is real but subtler, something that emerges over time.
When reading a synastry chart, give most weight to:
- Aspects under 3° orb (very strong)
- Aspects involving personal planets: Sun, Moon, Venus, Mars, and the Rising sign
- Conjunctions and oppositions (the most direct interactions)
AstroMystra's Oracle synastry reading automatically calculates all cross-chart aspects, ranks them by orb, and provides an AI interpretation of what the overall pattern means for your relationship.