Comparing two charts to understand the dynamic: attraction, security, challenges, the long term. Not a score — a reading.
Pro method (order of priority)Aspects between planets (the most important)Activated houses (where it plays out)Stability, passion, conflicts & repairs
Definition
Synastry is the astrological technique that compares two natal charts to analyse romantic compatibility, relational dynamics and tensions between partners.
Are you trying to understand astrological synastry and what it reveals about your relationship? Many people confuse sign compatibility with a true comparative study of the charts. This complete course guides you step by step through reading the aspects, the activated houses and the warning signs to watch for.
What is synastry in astrology?
Summary
Synastry compares two natal charts to see how two psyches interact.
It describes the dynamic: what attracts, what reassures, what irritates, what transforms.
It does not replace communication: it highlights the sensitive areas and the levers.
What it is not
A verdict (yes/no).
A simplistic compatibility test.
An excuse to accept the unacceptable.
How to do a synastry: professional method
Golden rules
1) Read each chart separately (maturity, wounds, needs).
2) Look at the luminaries (Sun/Moon) + ASC/DSC/MC/IC: foundation and relationship.
3) Set priorities: conjunctions/oppositions/squares, then trines/sextiles.
Houses 4/7/10 activated in a healthy way: home, couple, project.
Concrete examples of synastry reading
A “stable and lasting” synastry
Harmonious Saturn on Venus/Moon, fluid Mercury, angles touched without Neptune/Pluto domination: a built, reliable, long-term relationship.
A “passion + rollercoaster” synastry
Mars and Pluto very present, squares and oppositions: enormous magnetism, but a need for conflict rules and strict boundaries.
An “ideal… then hazy” synastry
Strong Neptune on Venus/Mercury: romance, projection, promises. It requires a reality hygiene: facts, timeline, concrete commitment.
Frequently asked questions about synastry
Synastry or composite?
Synastry = how two charts affect each other. Composite = “the chart of the relationship” as an entity. The two complement each other.
Can you “repair” a difficult synastry?
Yes, if both are mature: conflict rules, communication, boundaries, and a common goal. Otherwise, the hard aspects become repetitive.
What is the most important trio?
Sun/Moon + Mercury + Saturn. Without security, dialogue and reality… Venus/Mars is not enough.
Frequently asked questions about astrological synastry
What is the difference between synastry and a composite chart?+
Synastry compares two natal charts to see how each person affects the other. The composite chart merges the two charts into one and represents the relationship as an entity. The two approaches complement each other for a complete relational analysis.
Can a difficult synastry between two partners be improved?+
Yes, if both partners show maturity. With clear communication rules, respect for boundaries and a common goal, the difficult aspects become levers for growth. Otherwise, the tensions repeat themselves. See our course on planetary aspects to understand them better.
Which planets are the most important in synastry?+
The essential trio is Sun/Moon (emotional security), Mercury (communication) and Saturn (durability). Without these foundations, Venus-Mars aspects alone are not enough to maintain a stable relationship. Discover the role of each planet in our course.
Do you need the exact birth time for a synastry?+
The birth time is essential to know the Ascendant and the activated astrological houses. Without it, you can analyse the aspects between planets, but you lose the information about the areas of life concerned and the relational angles.