Mercury is one of the more difficult objects for amateur astronomers to observe because of its close proximity to the Sun. For the same reason, it is also one of the most fascinating and strange planets. Mercury is not much larger that our Moon, but orbits the Sun at an average distance of only 58 million km, compared to the Earth's 150 million km. On its sunlit side, Mercury's surface temperature can exceed 450C while the night side freezes at -180C.

Mercury has been the target of professional astronomers through the ages, and then of space probes, the most recent of which...