How to Read a Synastry Chart

Read the owners of the planets first

Before interpreting a line between wheels, write down whose planet is whose. “A’s Venus to B’s Mars” is different from silently assigning both symbols to a single person. Venus and Mars are topics in each person’s own chart; their cross-aspect is a possible point of exchange. The same geometry can describe two people negotiating affection, timing, preference, or autonomy in very different ways. Read the pair's actions before choosing any one story.

Check the angle and the orb

A conjunction centers on 0°, a square on 90°, a trine on 120°, and an opposition on 180°. An orb is the difference between the measured separation and that exact angle. Decide the cutoff before reading the list. The site's focused comparison defaults to 3° for major interaspects; a different orb setting can change which lines appear. A contact at 0° 20′ from exactness is geometrically closer than one at 2° 50′, but neither measurement says how enduring or healthy a relationship is.

Do not count every printed line as an independent story. One person's natal pattern can recur across several cross-aspects. Group contacts by theme and see whether different indicators point to the same question. A square can name a subject that requires negotiation; a trine can name an easy habit that no one has examined. Neither should be translated into “bad” or “good” people.

What if a birth time is unknown?

Separate the date from the hour. The Sun, Venus, and slower planets often remain useful at date precision, but any position close to a sign or aspect boundary deserves a range check. The Moon moves quickly enough that a near-cutoff lunar contact can appear or disappear over a plausible birth day. Without a dependable time and birthplace, do not use that person's Ascendant, Midheaven, or houses. Also avoid claiming that the other person's planet falls in a specific house of an untimed chart.

For an illustrative case, suppose A’s Moon might lie anywhere from 8° to 20° Cancer during an unknown day while B’s Saturn is at 18° Capricorn. The shorter separation could range from 170° to 178°. A 3° opposition cutoff would include some plausible times and exclude others. The honest reading is “possible opposition, time dependent,” not an exact relationship fact. Those numbers are an invented example, not a calculated birth chart.

A rounded recorded time and a historical daylight-saving offset are also sources of uncertainty. The birth-time window calculator can help inspect how one chart changes across a stated interval. A clock error may matter little for slow planets while moving an angle or house cusp substantially.

From a contact to a question

Use the aspect index and twelve guides for a concrete planet pair. Each guide includes the exact angle, a default orb, the birth-time caveat, and a question both people can answer. Read opposing interpretations together: the distinction between a conjunction and an opposition is geometric before it is literary.

After reading, formulate a question that can be discussed without astrology. For a Moon–Saturn contact, ask how the pair handles responsibility when one person needs comfort. For a Sun–Moon contact, ask who sets the pace of shared plans. For a Venus–Mars contact, ask whether affection and initiative are mutually welcome. The answers come from conversation and observation.