Synastry Aspects Guide: Planetary Connections in Relationship Astrology
Synastry is the astrology of relationships-comparing two natal charts to understand attraction, compatibility, and long-term potential. Learn to read the cosmic chemistry between any two people.
Luna
love & relationships specialist
In This Guide
What Is Synastry in Astrology?
Synastry (from Greek syn meaning "together" and astron meaning "star") is the comparative analysis of two natal charts to determine the dynamics, strengths, weaknesses, and potential longevity of a relationship. It operates on the premise that planetary positions at birth create an energetic signature-when two people interact, these signatures create a unique chemical reaction that defines the relationship.
Unlike sun-sign compatibility ("I'm a Scorpio, you're a Taurus"), synastry examines the actual geometric relationships between all planets in both charts. This reveals why some connections feel magnetic and others feel like friction, why certain people trigger your deepest fears, and why others feel instantly like family.
Before Comparing Charts
Always analyze each natal chart individually first. A person with natal Venus-Saturn square may struggle to receive affection regardless of synastry. Synastry cannot override the natal promise-it can only activate it.
Synastry vs. Composite vs. Davison Charts
Relationship astrology uses three main chart types, each revealing different dimensions of the connection:
Synastry
You vs. Me
Overlays two natal charts to show direct impact. Reveals daily friction, attraction, and communication styles.
Best for: Analyzing attraction, sexual chemistry, and specific psychological triggers
Composite
The 'We' Entity
Mathematical midpoints between partners' planets. Describes the relationship as a third, autonomous entity.
Best for: Understanding the relationship's destiny and social function-what you'll build together
Davison
Time-Space Midpoint
Creates a theoretical 'birth chart' for the relationship based on the midpoint in time and space between births.
Best for: Predictive work (progressions and transits) because it's rooted in actual coordinates
A couple may have harmonious synastry (getting along well personally) but a difficult composite chart, suggesting that while they like each other, the relationship itself faces external obstacles. Conversely, challenging synastry with a strong composite suggests a difficult daily dynamic that nonetheless feels "fated" to endure.
What Does Each Planet Represent in Synastry?
Not all planets carry equal weight. Personal planets (Sun through Mars) drive daily interaction and conscious attraction. Outer planets (Jupiter through Pluto) act as transformative forces:
| Planet | Function | Key Question |
|---|---|---|
| Sun | Identity, Ego, Purpose | Do our life paths and essential selves align? |
| Moon | Emotion, Habit, Home | Do we feel safe, nurtured, and comfortable together? |
| Mercury | Communication, Logic | Can we understand each other and solve problems? |
| Venus | Affection, Values, Taste | Do we like each other? Is there romantic harmony? |
| Mars | Drive, Sex, Conflict | Is there sexual chemistry? How do we handle anger? |
| Saturn | Structure, Commitment | Will this relationship last? Is there responsibility? |
| Jupiter | Growth, Joy, Beliefs | Do we expand each other's horizons? Is it fun? |
| Uranus | Excitement, Change | Is the bond stimulating or unstable? |
| Neptune | Romance, Illusion | Is there a spiritual bond or tendency to deceive? |
| Pluto | Transformation, Power | Is the bond deep and regenerating or controlling? |
The 5 Major Aspects in Synastry
Aspects are geometric angles between planets. In synastry, move away from "good vs. bad" thinking-instead consider "flowing vs. friction." Friction is necessary for growth and sexual tension; flow is necessary for comfort and longevity.
Conjunction (0°)
Fusion & Intensity
Planets at the same degree merge their energies. The most powerful aspect-creates unity but also blind spots.
Beneficial: Compatible planets (Moon conjunct Venus) create profound comfort and validation.
Challenging: Incompatible energies (Moon conjunct Saturn) can feel heavy, with the 'harder' planet dominating.
Opposition (180°)
Mirroring & Attraction
Planets directly across the zodiac create a tug-of-war. Generates immense attraction-opposites attract because they offer what the other lacks.
Beneficial: Promotes balance and integration of opposing viewpoints. Forces partners to meet in the middle.
Challenging: Can lead to standoffs or projection, where one partner disowns a trait and blames the other.
Trine (120°)
Harmony & Flow
Planets sharing the same element (Fire, Earth, Air, Water). Energy flows effortlessly without conscious effort.
Beneficial: Creates a safe haven. Sun-Moon trine = ego naturally supports emotional needs.
Challenging: Can breed complacency. The connection is so easy that couples may neglect growth.
Square (90°)
Friction & Action
Same modality (Cardinal, Fixed, Mutable) but incompatible elements. Creates dynamic tension demanding resolution.
Beneficial: Generates heat, passion, and momentum. Venus-Mars squares sustain long-term attraction.
Challenging: Without constructive channeling, manifests as arguing and frustration.
Sextile (60°)
Opportunity & Communication
Compatible elements (Fire-Air, Earth-Water). Similar to trine but requires active cultivation.
Beneficial: Encourages dialogue and offers an 'escape hatch' for tension from harder aspects.
Challenging: The weakest major aspect-easily ignored if couples don't put in effort.
What Orbs Should I Use for Synastry?
The "orb" is the allowable deviation from exactitude. In synastry, use tighter orbs than natal charts because energy must bridge two separate energy fields. The tighter the orb, the more intense the interaction:
| Category | Recommended Orb | Note |
|---|---|---|
| Luminaries (Sun/Moon) | 8°-10° | Powerful psychological pull felt across wider distance |
| Personal Planets (Mercury, Venus, Mars) | 5°-7° | Beyond this, chemistry may be weak |
| Outer Planets (Saturn through Pluto) | 3°-5° | Wide orbs = generational, not personal |
| Angles (Asc/Dsc/MC/IC) | 2°-4° | Sensitive to exact birth time |
Key Synastry Aspects to Check First
When analyzing a synastry chart, these combinations carry the most weight for romantic compatibility:
Sun-Moon Conjunction
Classic Marriage Aspect
The 'Cosmic Marriage.' The Sun illuminates the Moon's emotional world; the Moon nurtures the Sun's expression. Feels like coming home.
Venus-Mars Aspects
Primary Sexual Indicator
Conjunction/Trine: Romantic and sexual styles align naturally. Square/Opposition: Intense attraction with tension that sustains long-term passion.
Moon-Venus Conjunction
Domestic Bliss
You genuinely like each other and enjoy comforting one another. Softens the edges of any difficult aspects elsewhere.
Saturn to Sun/Moon/Venus
The Relationship Glue
No long-term relationship survives without Saturn contacts. They feel heavy but provide the container for the relationship to exist in reality.
Sun-Jupiter Aspects
Growth Factor
Jupiter acts as a cheerleader, expanding confidence and horizons. Brings luck, humor, and benevolence to the union.
The Saturn Paradox
Saturn aspects often feel heavy or restrictive-yet no lasting relationship survives without them. They're the "commitment glue" that keeps couples together when romance fades. Don't fear Saturn; embrace it.
House Overlays: Where Will I Feel You?
House overlays answer: "Where in my life will I experience this person?" Place Person A's planets in Person B's houses to see where the impact lands:
1st House (Self)
Direct, visceral
The House person feels fully 'seen.' Strong physical attraction indicator.
4th House (Home)
Familiar, intimate
Triggers deepest emotional security. Moon/Venus here = strong cohabitation desire.
5th House (Romance)
Fun, sparky
The overlay of dating, play, and procreation. Mars/Venus = intense sexual magnetism.
7th House (Partnership)
Marriage zone
House person views Planet person as ideal partner. Sun/Moon/Venus = classic marriage indicator.
8th House (Intimacy)
Intense, binding
Triggers psychological complexes and sexual merging. Feels fated but scary-hard to leave.
12th House (Unconscious)
Spiritual, hidden
Psychic link or past-life feeling. Common in secret affairs or unrequited love.
Heavy 8th house overlays create relationships that are difficult to leave. Heavy 12th house overlays often indicate secret affairs or psychic bonds that defy logic.
Special Points: Nodes, Vertex, Juno, Chiron
Beyond planets, calculated points offer insights into destiny, karma, and soul contracts:
Lunar Nodes (Destiny Axis)
North Node Contacts
Developmental-pushes you toward your destiny. Feels uncomfortable but promotes necessary growth.
South Node Contacts
"Past Life Connection." Instant familiarity but can trap you in old habits rather than evolving.
Vertex (Fated Encounters)
The "secondary Descendant" representing fated encounters beyond your control. When a personal planet conjuncts someone's Vertex, it triggers a life-altering meeting with a "before and after" quality.
Juno (Marriage Blueprint)
Represents your specific needs in a committed partner-distinct from Venus (romance) or Mars (sex). Juno conjunct Sun, Jupiter, or Ascendant indicates the partner fits your "spouse blueprint."
Chiron (The Wounded Healer)
Venus/Jupiter aspecting Chiron can soothe old pains through love. Mars/Saturn aspecting Chiron can re-traumatize. These relationships are often painful but offer profound psychological integration.
What Are Soulmate Indicators in Synastry?
In astrological terms, a "soulmate" is a partner with whom you share ease, mutual understanding, and support-distinct from the high-voltage intensity of twin flames. Look for these configurations:
Sun-Moon Conjunctions or Trines (masculine/feminine harmony)
Sun/Moon conjunct Ascendant or Descendant ('You are who I'm looking for')
Venus-Jupiter aspects (the 'feel good' factor-joy, luck, abundance)
Grand Trines involving both charts (closed circuit of harmony)
Strong 4th House emphasis (feeling of 'coming home' and safety)
Red Flag Aspects to Watch
No single aspect guarantees failure, but certain configurations require high maturity to manage safely. Without awareness, these can manifest destructively:
Mars-Pluto Square/Opposition
Power struggle of epic proportions. Can indicate domination or physical abuse if maturity is lacking.
Saturn-Moon Hard Aspects
Emotional starvation. Saturn creates a cold, critical environment where Moon feels unsafe expressing feelings.
Neptune-Venus Hard Aspects
High probability of deception or cheating. One partner may fall in love with a fantasy version of the other.
Uranus-Venus Hard Aspects
The 'Breakup Aspect.' Extreme instability-on-again/off-again preventing real security.
Red Flags ≠ Dealbreakers
These aspects require awareness and maturity, not avoidance. Many successful couples have "red flag" aspects-they've simply learned to channel the energy constructively. The danger comes from unconsciousness, not the aspect itself.
Frequently Asked Questions
What orbs should I use for synastry aspects?
Use tighter orbs than natal charts: 8-10° for Sun/Moon, 5-7° for personal planets, 3-5° for outer planets. The tighter the orb, the more intense and unavoidable the interaction.
Are squares and oppositions bad in synastry?
No-they're essential. Squares generate passion and momentum. Many long-term couples have Venus-Mars squares that keep attraction alive. Without friction, relationships can become stagnant.
What's the most important aspect for lasting relationships?
Saturn aspects. No long-term relationship survives without Saturn contacts to the Sun, Moon, or Venus. They provide the 'glue'-commitment and responsibility-even when romance fades.
Can synastry predict if someone is 'the one'?
Synastry shows potential and dynamics, not destiny. Great synastry with no effort fails; challenging synastry with mutual commitment can thrive. Free will always matters.
Should I use synastry or composite charts?
Both serve different purposes. Use synastry for attraction and day-to-day dynamics ('Do I like you?'). Use composite for the relationship's destiny and purpose ('What will we build together?').
What if we have no major aspects in synastry?
Check house overlays-they're equally important. Where someone's planets fall in your houses shows where you'll feel their impact. Also check special points like the Nodes and Vertex.
Calculate Your Synastry Chart
Ready to analyze your relationship? Generate a synastry chart to see the aspects between you and your partner.