We start December with one of the best chances to see Mercury this year, at least for the northern hemisphere. The elusive inner planet never strays far from the sun but this week it reaches the configuration known as the greatest western elongation.
This means that from our vantage point on Earth, the planet appears as far away as possible from the sun. It will appear in the pre-dawn twilight sky. For observers at mid-northern latitudes, the geometry is favourable, and so the best views are possible 30 to 60 minutes before sunrise.
The chart shows the view looking south-east from London at 7am GMT on 7 December. Although still low in the sky, Mercury will be unmistakably bright. As the darkness of the night gives way to the brightness of the day, the stars will fade from view one by one. Mercury will be the last to succumb.
The planet will be only marginally visible from the southern hemisphere. But for those up for a challenge, a clear eastern horizon will be essential to catch a glimpse. Binoculars could help reveal the planet but do not use binoculars around the time of sunrise. Catching even a glimpse of the sun can result in damaged eyesight.
