Synastry: Astrological Compatibility

Synastry is the art of comparing two birth charts. It reveals how two people’s energies interact and what kind of relationship dynamic they create.

Synastry doesn’t predict whether you’ll be together. It reveals the energetic compatibility and what you’re both learning from each other.

The Basics

When comparing two charts, you look at:

How each person’s planets aspect the other person’s planets
Whether their Sun, Moon, and Rising signs are compatible
Whether they have favorable or challenging house overlays

Harmonious Aspects Between Charts

Sun to Moon aspects: His Sun aspects her Moon (or vice versa). This is usually harmonious. One person feels understood by the other.

Venus to Venus: Similar love languages and values.

Mars to Venus: Sexual chemistry and attraction. Natural harmony between desire and love.

Sun to Sun: Similar core identities. Easy to understand each other.

Moon to Moon: Emotional compatibility. You “feel” each other.

Venus to Mars: Attraction. One person’s love draws the other’s desire. Passion.

Harmonious aspects between charts show where the relationship flows naturally.

Challenging Aspects Between Charts

Sun square Moon: Emotional and conscious wills clash. You don’t understand each other’s basic needs.

Venus square Mars: Love and desire conflict. Sexual and romantic tension.

Saturn to personal planets: One person (Saturn) feels responsibility for the other. Can feel restrictive.

Uranus to personal planets: Sudden changes and surprises. Unpredictable energy.

Pluto to personal planets: Intense, transformative, sometimes controlling energy. Power struggles possible.

Challenging aspects aren’t bad—they create the friction that leads to growth. But they require consciousness and effort.

House Overlays

When one person’s planet falls in the other person’s house, it activates that life area.

His Mars in her 7th house: He’s very present in her relationships. His energy is romantic or aggressive.

Her Venus in his 10th house: She supports his career. She’s publicly important to him.

His Saturn in her 5th house: He’s restrictive or serious about her creativity and romance. Can feel dampening.

Her Jupiter in his 8th house: She brings luck and expansion to his shared resources and intimacy.

Planets in partner’s houses show where they’re most present in each other’s lives.

The Sun-Moon Connection

The most important synastry aspect is one person’s Sun to the other’s Moon (or vice versa).

Sun conjunct Moon, trine, or sextile: One person feels deeply understood by the other. Natural harmony. He “gets” her emotionally.

Sun square or opposition Moon: Emotional and identity clash. He doesn’t understand her needs; she doesn’t understand his drive.

A strong Sun-Moon connection is considered one of the best compatibility indicators.

Venus-Mars Connection

Sexual and romantic chemistry:

Venus conjunct/trine Mars: Natural attraction and harmony. Sex and love flow together.

Venus square/opposition Mars: Sexual tension but also friction. High chemistry but also potential conflict.

Venus to Venus: Similar values and love styles. Compatible aesthetically and romantically.

A strong Venus-Mars connection shows sexual and romantic compatibility.

Complete Compatibility Picture

You’re not one aspect. You’re an entire chart interaction.

Example: She has Sun square Moon (internal conflict). He has Sun trine her Moon (he understands her). Their Venus-Mars squares each other (friction). His Saturn touches her personal planets (he’s restrictive).

Analysis: She’s internally conflicted, but he understands and supports her. Sexual chemistry is complicated. He can feel restrictive or controlling. They’re growing together through challenge.

This is a relationship that works but requires effort and understanding.

Assessing a Relationship

Look at:

Sun-Moon: Do you understand each other emotionally?
Venus aspects: Do you love similarly?
Mars aspects: Are you sexually compatible?
Saturn aspects: Where are the challenges and lessons?
House overlays: Where is each person in the other’s life?
Overall: Is there more harmony or challenge?

Neither is “bad.” Harmonious relationships are easy but might lack growth. Challenging relationships push you to evolve.

Composite Charts

Beyond synastry, there’s the composite chart—a chart created from the midpoint of both birth charts. It represents the relationship itself as its own entity.

A composite chart shows the relationship’s personality, challenges, and purpose separate from the two individuals.

Many couples find their composite chart helpful for understanding their relationship’s deeper meaning.

Red Flags

Astrology can illuminate dynamics but can’t detect abuse or toxicity.

Pluto dominant: Can indicate power struggles and control
Heavy Saturn: Can indicate limitation and restriction
Uranus strong: Can indicate unpredictability and instability

But none of these guarantee abuse. A responsible person with Pluto prominent can have a healthy relationship.

Trust your gut. Astrology illuminates; it doesn’t excuse harmful behavior.

Using Synastry

Get both charts. Compare them. Identify:

Harmonious aspects (flow naturally)
Challenging aspects (require work)
Important house placements (where each person matters)

Use this understanding to:

Appreciate your natural compatibility
Understand your friction points
Work consciously on challenges
Navigate the relationship with awareness

The best relationships aren’t the easiest ones. They’re the ones where two people choose each other and work through the friction together.