If you didn't spot Mercury last week, this week is your best opportunity. Mercury reaches its greatest distance from the Sun and its maximum height above the western horizon on the evening of March 22nd (for observers in North America and Europe), and it's nearly that high for the entire week.Jupiter is now getting low enough so that it's no longer a great signpost for Mercury, but the two planets still make a splendid pair a half hour after sunset. All you need is a clear evening and a viewing site with an good view down to the west horizon. The shore of a big lake (or ocean) would work well, as would the top of a tall building or hill. Note the spot where the Sun sets, wait another 15 minutes, and then start scanning above that spot for Jupiter and Mercury. Mercury is still about 12° — two binocular fields — above the horizon a half hour after sunset.
Starting around March 25th, Mercury plunges back toward the Sun, fades rapidly, and soon becomes hard to locate with the unaided eye. So take advantage of any clear evening to look for it as soon as possible!
In a telescope, Mercury is growing into a long, thin, crescent. It's 7" wide and 50% illuminated on the 20th, 8" wide and 30% illuminated on the 24th, and 9" wide and 20% illuminated on the 28th.
While you're looking at Mercury, remember that humankind has just achieved a historic first &mdash putting a spacecraft in orbit around the innermost planet. We will probably learn more about this enigmatic planet in the next few months than we've discovered so far in all of history.