Reference

Aspects

An aspect is the angle between two points in a chart. Two planets a third of the way around the wheel from each other are in a trine; directly across, an opposition. This site uses the five Ptolemaic aspects, and calculates them from real positions rather than by counting signs — which is why an aspect here can cross a sign boundary.

The five angles

The orb is how far from exact an aspect may sit and still count. There is no authoritative table; these are widely used moderate values, and they are wider for the aspects traditionally held to be strongest. The Sun and Moon are given two extra degrees, which is conventional.

What each one means

Each drawing shows that one aspect and nothing else: two bodies on a wheel, the ticks marking sign boundaries, and the shaded band showing how far the second may sit from exact and still count. No signs, no houses, no planets — an aspect is only an angle.

☌Conjunction

Two bodies at or near the same degree. The tradition reads this as fusion rather than as an exchange: planets in conjunction are described as acting according to their own natures, where planets in aspect act according to the nature of the aspect between them. The oldest sources do not count it among the aspects at all.

⚹Sextile

Two bodies 60 degrees apart, a sixth of the circle. Grouped with the trine as harmonious, because the signs involved are of the same kind, and counted in later sources among the favourable aspects.

□Square

Two bodies 90 degrees apart, a quarter of the circle — the quartile of the older sources. Counted among the disharmonious aspects on the same reasoning as the opposition: the signs involved are of opposite kinds.

△Trine

Two bodies a third of the way round the chart, 120 degrees apart — usually, though not always, in signs of the same triplicity. Named among the harmonious aspects, grouped with the sextile because the signs involved are of the same kind, and counted in later sources among the favourable ones.

☍Opposition

Two bodies directly across the chart, 180 degrees apart. Counted among the disharmonious aspects — in Ptolemy because the two signs are of opposite kinds, and in later sources among those classed as difficult rather than favourable.

Not every pair can form every aspect

This is astronomy rather than astrology. Mercury and Venus orbit inside the Earth’s orbit, so from here they never appear far from the Sun — which means some aspects between them simply cannot occur, in any chart, ever.

Measured rather than quoted: every body sampled monthly from 1900 to 2100 against the orbs above. Neptune and Pluto are the exception that proves the rule — they can reach a conjunction, but last did so in 1891, so no living chart contains one.

Aspects in your own chart

The birth chart page calculates every aspect between the planets in your chart, with its exact orb, from your date, time and place of birth. Nothing is transmitted; it is worked out on your own device.

What a particular pairing means

Everything above is about the angle alone. What the tradition actually says is about a particular pair of planets at that angle, and the Sun square the Moon is a different subject from the Sun square Saturn. Those readings are here, each traced to a work and a page — a few of a possible 372 so far, with the rest being sourced.