Interactive chart wheels encourage exploration because a symbol can be selected in place. The useful question is what the selection actually measures. On this site every contact panel names the two points, their tropical longitudes, the shorter angular separation, the nominal major aspect, and the orb. The prose below that measurement is an original symbolic interpretation. It cannot establish behavior, consent, compatibility, or a future event.
Start with two dated planetary positions
Each record includes a local calendar date, a recorded clock time when known, and historical UTC offset. The unknown-hour option substitutes local noon only as a calculation convention; the affected person’s Moon is omitted from synastry and the composite Moon is omitted altogether. The browser converts it to a UTC instant, then uses Astronomy Engine to calculate apparent geocentric positions on the true ecliptic and equinox of that date. The longitude is displayed in the tropical zodiac, where Aries begins at 0°. A longitude of 42° is 12° Taurus. The Moon can change several degrees in a day; an unknown hour can alter its sign or push a near-threshold aspect across the chosen orb. Other planets can also move enough to alter a near-threshold contact, so noon-based results remain approximate. A historical daylight-saving error can also change the UTC instant.
The form does not ask for birthplace coordinates. Planetary longitudes can be calculated without them, but a local Ascendant, Midheaven, and house system cannot. Do not read houses or angular contacts into this wheel. For those techniques, use a located birth chart or the separate composite calculator, where the house method is declared.
What a cross-chart contact says
Synastry preserves which person owns each point. The tool compares every planet from Person A with every planet from Person B, retaining contacts within the chosen maximum orb. It measures the shorter distance around a circle, from 0° to 180°. Conjunction is exact at 0°, sextile at 60°, square at 90°, trine at 120°, and opposition at 180°. The orb is the absolute difference from the selected exact angle. For example, a 122.4° separation is a trine with a 2.4° orb and appears under 3° or 5°, but not 1°. Some astrologers prefer wider limits; these three settings are display choices rather than objective thresholds.
Clicking the planet itself describes its role in that specific person’s chart. Clicking a line item shows the measured relationship between two distinct positions. Sun–Moon can invite a conversation about direction and daily emotional pace; Venus–Mars about values and action; Moon–Saturn about comfort and responsibility. These are questions to investigate in the relationship. A square does not prove conflict, and a trine does not prove an easy or safe bond. A single contact says little without both natal charts and lived circumstances.
What the midpoint composite says
The composite takes corresponding natal points and finds the halfway position along the shorter zodiac arc. It is useful to imagine a relationship as a third symbolic pattern, while remembering that this pattern is not a real sky at a real time. An exact 180° separation has two equally short ways around the circle and therefore two equally valid midpoints. The explorer displays both candidates and excludes that point from the composite aspect list. A pair very close to opposition can switch midpoint sides after a small correction to one birth record; inspect the natal longitudes before interpreting such a point.
Composite aspects are measured between the derived midpoint longitudes using the same five major angles and orb settings. A selected composite planet describes a theme for the pair; a selected aspect links two themes. It does not assign an experience to Person A or B individually. That distinction matters: a composite Sun–Moon contact and a synastry Sun–Moon contact are different calculations and should not share a stock interpretation. A Davison relationship chart differs again because it calculates a real sky at a midpoint time and place.
Read a result in context
The two-card overview selects the closest measured contact and one from a different planet pair within the chosen orb. Its prompts name what was measured; they do not tally supportive or difficult angles into a verdict. Begin with the printed geometry and the reliability of the two birth records. Use a narrower orb when many contacts make the list hard to read. Check the Moon cautiously if either hour was rounded or recalled. Then read several contacts in both directions; Person A’s Venus to B’s Mars is not the same ownership as A’s Mars to B’s Venus. Ask a concrete question rather than treating an aspect label as a verdict. What agreement is working? What did each person actually ask for? Which boundary has been stated and respected?
A clickable chart is a navigation aid through calculated symbols. It has no access to the pair’s history, conduct, expectations, or consent. Its best use is to organize conversation and further reading. Open the interactive partner chart →