Every aspect between two birth charts, the house overlays in both directions, and the contacts that repeat back and forth — with no compatibility percentage, because there is no honest way to compute one.
Tropical longitudes from a real ephemeris · cross-chart aspects re-derived against a second, independent ephemeris on every test chart
A natal chart is one sky, frozen at one birth. Synastry lays a second sky over the first and measures the angles between them: her Moon against his Venus, his Mars against her Saturn, and so on through the whole grid. Those angles are the same ones read inside a single chart — conjunction, sextile, square, trine, opposition — but here each one connects two people rather than two parts of one person.
The orbs on this page are the same orbs the natal aspects page uses: wider for the Sun and Moon, tighter for the outer planets, tighter again for the minor aspects. That is deliberate. If synastry quietly used a looser table, the same two degrees of separation would be an aspect on one page of this site and not an aspect on another.
Direction is kept. Her Venus on his Saturn and his Venus on her Saturn are two different statements, and only one of them may be true in a given pair. The full grid is computed both ways round rather than folded into a symmetric list, so the result says whose planet is doing what.
The second half of a synastry reading is not about aspects at all. It asks which of your houses their planets fall into — their Sun in your tenth, your Moon in their seventh. Houses are cut from the Ascendant, and the Ascendant moves roughly one degree every four minutes, which is why an overlay needs a real birth time rather than a convenient one.
When a time is missing, this page removes that person's Ascendant, Midheaven and overlay instead of taking them from noon. A noon Ascendant is not a rough answer; it is a precise answer to a question nobody asked, and it reads exactly as confidently as a correct one. The planet-to-planet aspects still work, because most planets move too slowly for a day to matter — with the Moon as the standing exception, and the result says so.
Almost every synastry tool prints a compatibility score. The temptation is obvious and the arithmetic is easy: weight the trines positively, the squares negatively, add them up, divide. The problem is that the weights are invented. No two schools agree on what a Venus trine is worth against a Saturn square, and the same two charts will score anywhere across a wide range depending on which weighting a site happened to choose.
So this page reports counts instead: how many contacts, how many harmonious, how many tense, how many are exact to within a degree, and how many involve two personal planets rather than two slow ones. Those are facts about the two charts. What they add up to is a judgement, and it belongs to the people involved rather than to a formula.
The squares are worth a word of their own. A tense count is not a bad score. Hard aspects between two charts are the ones that produce friction, attention and change, and long relationships tend to have plenty; grids made entirely of trines are often described by the people in them as pleasant and inert. The counts describe the texture of a contact, not its worth.
When the same two bodies aspect each other in both directions — her Moon to his Venus, and his Moon to her Venus — astrologers call it a double whammy, and treat it as heavier than either contact alone, because the theme arrives from both sides at once. They are listed separately in the result rather than left for you to spot in a fourteen-by-fourteen grid.
Different traditions asking different questions. Guna Milan compares two sidereal Moons against eight classical tables and returns a score out of 36; it is fast, narrow, and deliberately Moon-only. Synastry is western and tropical, and compares every body in both charts plus the house overlays. Neither replaces the other, and a pair can look strong in one and mixed in the other. Both calculators are on this site.
The ones that are tight and involve personal bodies. A Sun, Moon, Mercury, Venus or Mars contact inside a degree or two describes something people actually notice; a Neptune-Pluto contact between two people born the same decade is shared by millions and says little about the pair. The result marks both, so the tight personal contacts sort to the top.
Partly. Tick the box and the planet-to-planet aspects are still computed, since most planets move slowly enough that a day makes little difference. What disappears is that person's Ascendant, Midheaven and house overlay, and the Moon becomes approximate — it can cover half a sign in a day, so a Moon contact from a timeless chart may be wrong.
No. Hard aspects describe friction and the pull that comes with it, not an outcome. Plenty of long marriages are full of squares and oppositions, and plenty of easy grids belong to people who drifted apart. Nothing on this page predicts events.
Usually orbs. There is no universal table, so a site using nine degrees for a Sun square will list contacts a site using seven does not. Occasionally it is the bodies included — some tools add asteroids or the vertex — or a different house system, which changes the overlays but not the aspects.
Both ways, and they say different things. This page shows each direction separately: their bodies in your houses, and yours in theirs.