This week, on September 5, Mercury will reach the astronomical configuration known as greatest western elongation. This is the point at which Mercury will be at its farthest point west of the sun, as seen from Earth. This provides an excellent opportunity to catch a glimpse of the elusive planet.
A greatest western elongation event means the planet will be visible in the sky before sunrise. The chart shows the view looking east-northeast at 05.30 BST on the morning of 5 September. It 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.
Mercury is a challenging target because it never rises high in the sky before the sun comes up, but it will outshine all the other stars around it in the pre-dawn sky.
The planet is also visible from the southern hemisphere, although its height above the horizon is not as favorable for this particular elongation.
After this elongation, Mercury will move behind the sun through its orbit. It will next become visible in November and reach its greatest eastern extension on November 16. In this configuration it will be visible in the evening sky.
