Two charts. Every aspect.

Synastry overlays two birth charts to see how each person's planets fall in relation to the other's. Where Person A's Moon lands close to Person B's Venus, there's a conjunction — a fusion of emotional needs and the relating style. The full set of inter-chart aspects (conjunctions, squares, trines, oppositions, sextiles) gives a detailed map of where two people easily harmonize, where they grow through friction, and where the dynamic has depth. It is not a yes/no compatibility score; it's a portrait of what the specific relationship is made of.

Every detected inter-chart aspect within a 6° orb, sorted by tightness (tightest is strongest). Each aspect gets a practitioner-written interpretation that names the relationship dynamic at stake. A weighted compatibility score (intensity + harmony index, not a romance algorithm). A short composite teaser; for the full composite-chart reading, run the composite chamber separately.

Yes. As of v2.215, every astrology tool on the site is free except Ask Your Chart (cash, $4.99 / 5-pack $19.99). Synastry computes both charts at arcsecond precision, detects every inter-chart aspect, runs the weighted scoring, and renders the practitioner-written interpretation for each contact — all free, saved to your reading history.

A weighted tally of inter-chart aspects — harmonious (trines, sextiles) count positively, challenging (squares, oppositions) count against, conjunctions count neutrally but get weight for intensity. Treat it as a rough intensity/harmony index, not a verdict. Relationships with 'low' scores can be profound and durable; relationships with 'high' scores can be lazy. The aspects themselves and their interpretations matter more than the number.

For planet-to-planet contacts (Sun, Moon, etc. interacting with each other), birth time has modest impact — the Moon moves about 13° per day, so a several-hour error can shift its sign in an edge case. For Ascendant and house placements, birth time is critical (the Ascendant rotates through all 12 signs every 24 hours). If you have reliable times for both partners, the reading sharpens. If one partner's time is unreliable, the planet-to-planet aspects still tell most of the story.