Chinese compatibility reading and Western synastry both compare two birth charts, and both will hand you a verdict. They get there from completely different places, which is worth knowing before you trust either.
What each one is built on
| He Hun | Western synastry | |
|---|---|---|
| Core data | Four pillars: year, month, day, hour | Planet positions by sign and house |
| Language | Five elements, ten gods | Aspects, elements, modalities |
| Method | Relational — each chart read against the other | Angular — geometric relationships between charts |
| Timing | Ten-year luck pillars, annual pillars | Transits and progressions |
The structural difference
Synastry is geometric: it looks at the angles between planets in two charts. He Hun is relational and hierarchical: it fixes a reference point (the Day Master or the palace element) and names everything else by how it stands to that point. The first asks "what angle"; the second asks "what relationship".
This is also why He Hun can produce a result from a date and time alone, whereas synastry needs a precise location as well. The Chinese system is built on a cyclical calendar rather than on positions in space.
Why they disagree
They are measuring different things, so a couple can read well in one and poorly in the other without either being wrong. Be sceptical of any tool that merges them into a single score — the underlying categories do not map onto each other cleanly.
Which to use
Use whichever framework you can actually think inside. A system whose vocabulary you have to keep translating is not giving you much. And either way, treat the output as a prompt for a conversation rather than an answer to one.
Why the categories do not map
It is tempting to translate between the two — to treat the Day Master as a sun sign, or the Ten Gods as aspects. That translation does not survive contact. The Day Master is a reference point chosen by convention; a sun sign is a position in space. An aspect is an angle; a god is a relation.
This is why a merged score is not meaningful. The two systems are not measuring the same thing at different resolutions; they are measuring different things.
A practical difference
Because He Hun works from a calendar rather than from positions in space, it needs only a date and a time. Synastry needs a place as well, and is sensitive to errors in it.
That makes the Chinese system easier to apply when records are incomplete, which is more often than you would expect.