Mercury is a fascinating but widely neglected planet. With the most eccentric orbit of any planet except Pluto, Mercury lies two-thirds as far from the Sun at its closest as at its farthest; therefore, it varies greatly in brightness from one apparition to another.

With the help of binoculars, Mercury should be visible briefly as a rosy faint star. But the scene an be far more dramatic with a telescope. Appearing like a smaller version of the Moon, Mercury's phases are visible in a 3-inch (76-millimeter) scope at 100x if the seeing is good. Although it has a reputation as a difficult telescopic target, Mercury is the only planet besides Mars to show details on a solid surface.

Ideally, Mercury should be viewed in daylight, when it is higher above the horizon than it ever can be during twilight. This is much easier during a morning apparition than an evening apparition; you can locate Mercury in the twilight and then follow it well after the Sun rises. (Of course, you must take great care not to point the scope at the Sun by accident.) In daylight, use a red or an orange filter to make the blue sky darker and increase the contrast. Mercury has high surface brightness, so it responds well to high magnifications. Look for bright and dark surface markings, especially along the day-night terminator.