PICK OF THE MONTH
MERCURY
BEST TIME TO SEE: 15 March, 18:50 UT ALTITUDE: 11º LOCATION: Pisces DIRECTION: West FEATURES: Phase, subtle markings EQUIPMENT: 75mm or larger
Mercury has a close encounter with dazzling Venus in the evening sky on 3 March as it moves toward a very favourable eastern elongation midmonth. Both planets appear separated by just over 1° on 3 and 4 March, with mag. –3.8 Venus outshining its inner neighbour with ease.
Mercury is bright though, shining at mag. –1.1. Greatest eastern elongation occurs on 15 March when Mercury, now at mag. –0.1, sets nearly two hours after the Sun. This means it’ll be visible against reasonably dark skies with Venus remaining nearby. On 18 March, mag. +0.4 Mercury, mag. –3.8 Venus and a 1%-lit waxing crescent Moon form a line in the sky, with Mercury at the top and the Moon at the bottom.
This is a great time to try and get a telescopic view of Mercury as its phase is now decreasing. On the evening of the 18th, the planet can be seen as an 8 arc-second-diameter crescent, 31%-lit. Typically, and despite its favourable location, Mercury’s light has to pass through a turbulent layer of atmosphere close to the horizon. Consequently, this small crescent often suffers from the wobbles and looks quite distorted. Venus and Mercury jostle for position as the highest evening planet over the following days, Venus eventually winning the crown during the last week of the month. Mercury also begins to fade but remains nicely visible thanks to its extremely favourable location with respect to the Sun. On 23 March it appears as a mag. +1.8 dot 6° to the lower right of Venus. A telescope will show it as a slender 13%-lit crescent, 9 arcseconds across on this date. After the 23rd, Mercury moves ever closer to the Sun at an increasing rate ahead of it reaching inferior conjunction early next month.