The rainbow axis is an imaginary straight line that connects the light source, observer and anti-solar point.
- The centre of a rainbow is always on its axis.
- The centre of a rainbow always corresponds with the anti-solar point.
- When drawing a diagram showing the axis of a rainbow, the Sun and anti-solar point, are at opposite ends with the observer between them.
- From an observer’s point of view, the rainbow axis is an imaginary line that they look along towards the centre of a rainbow.