Two planets 180° apart, on opposite sides of the chart: they pull in contrary directions.
It describes tension between two equally legitimate needs — independence and attachment, say. It is often lived as oscillation, or by projecting one half onto other people. It is not a flaw to be corrected: it is an axis you learn to stand on.
Reading it in your chart
In your chart an opposition links two planets straight across the wheel, usually from complementary signs: Aries and Libra, Taurus and Scorpio, Cancer and Capricorn. Each pair of opposite signs shares the same mode and joins elements that complete each other, fire with air, earth with water. So the two ends are not enemies: they speak about related themes from opposite angles.
The axis of houses it falls on matters just as much. An opposition between the first and seventh houses is about you and other people; between the fourth and tenth, about home and career. SideraMea counts an opposition up to 8° either side of exact: the tighter the orb, the more strongly the tension is felt.
How it differs from a square
Oppositions and squares are both hard aspects, but they work differently. A square sets two functions at cross purposes: they get in each other's way and force you to act. An opposition puts them face to face: they see each other, measure each other, and one of them is often handed over to someone else. With Venus opposite Saturn, for instance, you might keep meeting partners who seem cold or strict, without recognising how much of that caution is also yours.
That is why the opposition is traditionally read as the aspect of awareness and relationship. The work it points to is not choosing a side, but finding a moving balance in which both needs get their turn.
Frequently asked questions
Is an opposition in a birth chart bad?
No. In astrology no aspect is good or bad in itself. An opposition describes two needs pulling in contrary directions, which can show up as swinging between extremes or as friction with other people. It is also the aspect that most helps you see yourself from the outside: learning to hold both ends often brings balance and a real gift for mediation.
What does a transit opposite a natal planet mean?
It means a moving planet has reached the far side of the wheel from one of your natal planets. Traditionally this is read as a time when something personal is brought face to face with the outside world: people, demands or situations that act as a mirror. Transits use tighter orbs than the birth chart, around 3°.
What does it mean to have lots of oppositions in your chart?
When several planets sit on two opposite sides of the chart, the chart is built around an axis, and life tends to swing between two poles like a pendulum. Astrologers usually suggest noticing which half feels like yours and which you tend to look for, or criticise, in other people. That second half is often the part asking to be integrated.
See it in your own chart
Calculating your birth chart is free: wheel, planets, houses, aspects and a first reading. All you need is your date, time and place of birth.