Starwatch: Mercury reaches its greatest western elongation

Early risers will get a prime opportunity to glimpse the planet as it moves to its furthest point west from the sun

This week, on 5 September, Mercury will reach the astronomical configuration known as greatest western elongation. This is the point at which Mercury will be at its furthest point west from the sun, as viewed from Earth. It offers a prime opportunity to catch a glimpse of the elusive planet.

A greatest western elongation event means that the planet will be visible in the sky before sunrise. The chart shows the view looking east-north-east at 05.30 BST on the morning of 5 September. This is about 50 minutes before sunrise. Find a spot with a clear view of the horizon, and as far away from any street lights as you can.