Mercury is putting in its best evening appearance of the year for mid-northern skywatchers.
An old legend, almost certainly false, is that Copernicus never saw the planet Mercury. It's easy to see how the story took hold. Nicolas Copernicus was mostly an indoor astronomer, wrestling with math and generally using other astronomers' observations to work out his revolutionary model of the solar system. But at his northerly latitude on the shore of the Baltic Sea, amid the local fogs and mists that he often complained about, the closest planet to the Sun may indeed have been an unusual sighting.
Mercury is in fact the last bright planet that many skywatchers identify. It spends most of the time deep in the glow of sunset or sunrise. But now is different. Mercury has come out of hiding to put on perhaps its clearest show of the year for mid-northern viewers. It will be at its best from about January 24th to February 4th. It will appear highest on January 31st (if you're near 40° north latitude), more than 10° above the west-southwestern horizon a half hour after sunset and setting only as the sky grows fully dark.
To see Mercury, go out shortly after sunset to a spot with a good view toward west. The planet should glimmer into view within a half hour after sunset. It will appear to brighten as the sky darkens. But if you’re using a telescope, try to view Mercury as soon as you can find it, before it gets too low and fuzzy in the thick atmosphere near the horizon. Mercury’s disk will be gibbous at first, half lit on January 31st, and a thick crescent in early February.
Should you miss the planet during this apparition, it will put on another good evening show in late May, low in the west-northwest with Jupiter above it.