Synastry

What it is

Synastry is the astrological technique that compares two birth charts. It doesn't look at each person separately —the birth chart already does that— but at the angles the planets of one form with the planets of the other. Those angles are called aspects, and they're what describes the dynamic between two people.

What aspects are

An aspect is the angular distance between two planets. The five main ones:

• Conjunction (0°): the two energies merge. Intense, neither good nor bad.
• Sextile (60°): an open door you still have to push.
• Square (90°): friction. Uncomfortable, and that's why it makes you grow.
• Trine (120°): flows on its own, almost unnoticed.
• Opposition (180°): two forces facing off, asking for balance.

Every aspect has an orb: how many degrees it is from exact. The smaller it is, the more you feel it. A trine half a degree from exact weighs far more than one six degrees off.

Which planets matter in a relationship

Sun and Moon are the axis: identity and emotional world. Venus and Mars speak of attraction and desire. Mercury, of whether you understand each other when you talk. Saturn, of commitment and limits. And the Ascendant, of first impressions — but only if both people know their time of birth.

The slow planets —Uranus, Neptune, Pluto— are left out: between two people of similar age they sit at almost the same degree, so they say nothing about this particular bond.

Why to distrust the compatibility percentage

Plenty of apps hand you a number: 87% compatible. That number means nothing. There is no astrological formula that produces a percentage, and putting a figure on a relationship does the worst thing a reading can do: close the conversation instead of opening it.

What can honestly be said is how many contacts there are, which ones flow, which ones chafe and how exact they are. That's information. A verdict isn't.

A caution almost nobody mentions

In a synastry there's a second person who isn't asking. A serious reading talks about the bond and about the person consulting — it never states what the other person thinks, feels or will do, and never rules on whether the relationship should continue or end. That isn't read in a chart: it's decided between two people.

Arcana's version

Arcana calculates both charts with real ephemerides and shows the contacts one by one, with their type and their orb. The bars measure how exact each aspect is — not how much two people love each other — and that's spelled out on screen. There's no compatibility percentage, on purpose.