Mercury is not an easy target to observe. The innermost planet in our Solar System is never further away from the Sun than 30 degrees. It is either trailing the Sun and disappearing below the horizon just after sunset or moving ahead of the Sun and visible just a short time before sunrise.
One good opportunity to observe Mercury under good conditions will happen on 16 February when it reaches its maximum elongation (apparent angular distance) of 18 degrees.
However, a much more spectacular view (weather permitting!) will be offered on the Friday before, on 8 February, when Mars and Mercury will be separated in the sky by only 20 arc minutes (for comparison, the Moon has an apparent size of about 30 arc minutes).
Both planets will be quite bright: Mercury with magnitude -1, which is as bright as the brightest stars, and Mars a bit fainter with a magnitude of +1. However because it will happen right after sunset, the contrast is low and you had best choose a place where the horizon in the Western direction is not obstructed by trees or buildings. Then you should be able to see the two planets at a very low elevation after it has become quite dark.
In fact, members of ESA’s Mission Analysis Team from ESOC in Darmstadt, where I work, are planning a viewing on that evening – and you’re welcome to take part!
The rough plan is to meet in the Darmstadt area and then head to a hillside by about 18:30 or so. If you’d like to join us, please send mail to me, email@example.com, and we’ll confirm the plan. And hope for good weather!
Editor’s note: Thanks to Michael Khan for the information taken from his blog and the image, which was produced using Stellarium.
If you would like to know more about ESA’s plans to observe Mercury from up close, access the BepiColombo pages in the ESA website and find out what experiments our space probe (to be launched in 2015) will carry to this difficult-to-observe planet.