Western Astrology Aspects: Conjunction to Quincunx, with Orbs

In short: A Western aspect is an angle between two points in the zodiac, measured in degrees and allowed a margin called an orb. The five classical aspects come from Ptolemy: conjunction (0°), sextile (60°), square (90°), trine (120°) and opposition (180°). Johannes Kepler added minor aspects in the seventeenth century, and modern astrologers widely use the quincunx (150°). Trines and sextiles are read as easy, squares and oppositions as dynamic, and conjunctions as a blending whose tone depends on the planets.

The aspects

Orbs are conventions, not laws. Medieval astrologers such as William Lilly assigned orbs to the planets (the Sun's being largest) rather than to the aspects; modern practice usually assigns them by aspect, widening them for the Sun and Moon.

Ptolemy's aspects and why they are those angles

Ptolemy (Tetrabiblos I.13) explained the classical aspects through the geometry of the signs: the trine joins signs of the same gender and triplicity (element); the sextile joins signs of the same gender; the square joins signs of opposite gender; the opposition joins signs on the same axis. (In his separate Harmonics he related such divisions to musical intervals.) The conjunction was not strictly an aspect for Ptolemy — the planets are simply together — but it has always been treated as the strongest connection.

Kepler's additions

Johannes Kepler, the astronomer who discovered the laws of planetary motion, was also a reforming astrologer. He proposed new aspects based on harmonic divisions of the circle — the quintile and biquintile (72°, 144°), the semi-square and the sesquiquadrate (45°, 135°) among them — and argued that aspects work by geometry rather than by sign. The semi-sextile and quincunx entered common use later; the quincunx became central in twentieth-century practice.

Applying and separating

An aspect is applying when the faster planet is moving toward exactness and separating after it has passed. Traditional and horary astrology give great weight to the difference: an applying aspect describes something developing, a separating one something passing. Modern natal astrology often treats the two alike, though many astrologers feel applying aspects are stronger.

Aspects by sign and by degree

The Hellenistic astrologers whose work underlies Western astrology counted aspects primarily by whole sign: a planet in Aries "witnessed" planets in Gemini, Cancer, Leo, Libra, Sagittarius and Aquarius, whatever the degrees. Modern Western practice measures degrees, which means two planets can be in trine by degree while sitting in signs of different elements — an "out-of-sign" or dissociate aspect.

Vedic astrology counts aspects by sign as well, but with its own special aspects (see graha drishti).

In synastry and transits

Aspects are the core of synastry (comparing two charts): Venus–Mars, Sun–Moon and Moon–Moon aspects are read for attraction and emotional fit, Saturn aspects for commitment and weight. In transits, slow planets' aspects to natal planets are the main timing tool. See our Sun-sign compatibility pages for the sign-level version of the same idea.

The major aspects in detail

• The sextile — 60°, opportunity
• The square — 90°, tension and action
• The trine — 120°, ease and talent
• The opposition — 180°, polarity and relationship

FAQ

What orb should I use? There is no single correct orb. A common modern scheme is 8–10° for conjunctions and oppositions, 6–8° for squares and trines, 4–6° for sextiles and 2–3° for the quincunx, wider when the Sun or Moon is involved.

Are squares bad? No. They are read as tension that motivates action. Many accomplished people have prominent squares.

Are trines always good? They are read as easy, which can also mean unused. A trine gives talent; effort turns it into skill.

Written by Sunyra Editorial. Astrology is a tradition of interpretation; read this as guidance, not a forecast. Disclaimer.

Last reviewed 20 October 2026