Reference · Astrology
What is an opposition?
Kevin Blaxton — software builder; astrology student for 40+ years · figures computed by the OrbHeaven engine
Published · Last revised
An opposition is the aspect of 180°: two planets exactly across the zodiac from each other, six signs apart. It is the widest an aspect can be — half the circle — and the tradition reads it as a tension between two sides that both want a hearing.
What is an opposition?
Geometrically it is an aspect of 180° — two planets at opposite ecliptic longitudes, so they lie in opposite directions along the zodiac from the Earth and rise and set roughly twelve hours apart. It is the largest angle the aspects measure; beyond 180° the separation starts to close again.
The Full Moon is the clearest example: the Sun and Moon in exact opposition, the Earth between them.
How it is counted: the orb
An exact opposition is 180°. OrbHeaven counts one when the two planets are within 8° of that in a birth chart, or 9° when the Sun or Moon is involved — the same generous orb as the conjunction. The figure shows the angle and that orb, taken from the engine’s table.
What it is read as
Interpretation, labelled as such: an opposition is read as a polarity — two planets pulling in opposite directions that must somehow be balanced, often experienced through other people or through swinging between two poles. It is classed with the “hard” aspects, read as dynamic rather than easy.
A short history
The opposition is one of the classical Ptolemaic configurations, derived from dividing the circle in two — the signs six apart, which “behold” each other across the chart. It has been counted as a major aspect in every era of Western astrology.
Common misconceptions
- Is an opposition the same as a conjunction on the opposite side?
- It is the aspect of 180° — two planets opposite each other. Like the conjunction it gets a wide (8°) orb, but it is read as a tension between two poles rather than a fusion.
- Is every Full Moon an opposition?
- Yes — a Full Moon is by definition the Sun and Moon in opposition (180° apart). Not every opposition is a Full Moon, though; any two planets can form one.
References & further reading
- [1] Ptolemy, Tetrabiblos (2nd c. CE) — the opposition among the classical configurations.
- [2] Tompkins, S., Aspects in Astrology — the modern interpretation of the opposition.
- [3] OrbHeaven engine (astronomy-engine), aspects module — the 180° angle and the 8°/9° natal orb; re-derived in aspects-demo.test.ts.
Suggested citation
Blaxton, K. (2026). What is an opposition. OrbHeaven Reference. https://orbheaven.com/reference/the-oppositionRevision history
- First build (concise). Shared aspect-shape diagram (180°, engine orb); links up to the Aspects hub, Orbs and The Full Moon. Geometry, orb computation, tradition and history kept separate. No interactive.
Related glossary entries
About a minute. Birth time optional, and no account until after you have seen it.
More in the reference library
What is an aspect in astrology? The angles, the orbs, and the geometry
An aspect is the angle between two points in a chart. This is the geometry — the six angles astrologers use, what an orb is, and where the set comes from — with an interactive dial that classifies any separation using OrbHeaven’s engine.
What is an orb in astrology?
An orb is how far an aspect is from exact — and how far from exact still counts. This explains the arithmetic, OrbHeaven’s orb table and the luminary rule, with an interactive dial, and that orbs are a convention of practice, not a scientific threshold.
What is a full Moon?
A full Moon is the instant the Sun and Moon reach about 180° apart in ecliptic longitude — an opposition, the Earth between them and the near side fully lit. With the geometry, a worked example from the engine, and why most full Moons are not lunar eclipses.