This diagram shows the elongations (or angle) of the Earth's position from the Sun.

Elongation is an astronomical term that refers to the angle between the Sun and a planet, as viewed from Earth.

When an inferior planet is visible after sunset, it is near its greatest eastern elongation. When an inferior planet is visible before sunrise, it is near its greatest western elongation. The greatest elongation (west or east), for Mercury, is 28°; and for Venus, 47°.

See also: astronomical conjunction