Synastry
Synastry is the astrological comparison of two natal charts: the aspects between one person's planets and the other's are calculated to look at the dynamic of a relationship.
The name comes from the Greek syn ("together") and astēr ("star"). Technically, two natal charts are laid over each other to check which angular relationships arise between them: is one person's Moon in trine to the other's Venus? Does Saturn here form a square to the Sun there? These inter-aspects are synastry's core material; some schools additionally look at which houses a partner's planets fall into — which requires both birth times to be known, though.
The aspects are read by the same inherited principles as in an individual chart: trines and sextiles as an easier connection, squares and oppositions as friction, conjunctions as a bundling of both people's themes. None of that establishes the quality or the duration of a relationship; synastry is an astrological framework for reflection, not a measurement of a relationship.
Synastry is not a compatibility test with a percentage score, and not a forecast of success or failure. Within the astrological system it describes relationship themes — the relationship itself is decided by the people in it.
How we use this term
In synastry, Leitstern calculates the individual aspects between two natal charts and shows their names and orbs. There's no percentage score and no blanket match rating.
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