Tonight – March 18, 2018 – if you’re far enough west with respect to the International Date Line, and especially if you’re in the Northern Hemisphere, you’ve got a good shot at seeing the whisker-thin young waxing crescent moon joining up with the planets Mercury and Venus after sunset. That’s true even though – according to your calendar – the new moon came just yesterday, on March 17.
By the way, if you spot Venus, the third-brightest celestial body after the sun and moon, popping out into the western dusk – but not Mercury – aim binoculars at Venus. Then seek for Mercury in the same binocular field with Venus. From northerly latitudes, however, you have a good chance of spotting Mercury with the eye alone.
The moon turned new on March 17 at 13:12 UTC. That means that – if you’re in a North American time zone – new moon came yesterday morning, March 17 (10:12 a.m. ADT, 9:12 a.m. EDT, 8:12 a.m. CDT, 7:12 a.m. MDT, 6:12 a.m. PDT, 5:12 a.m. Alaskan Time and 3:12 a.m. Hawaiian Time).
Thus, as the sun sets over North America and the United States on March 18, the moon will be roughly one and one-half day old. It’ll be over 24 hours old for Europe and Africa, yet less a day old for eastern Asia, Australia and New Zealand. The younger the moon, the greater the likelihood that you’ll have to wait until March 19 to view it – especially from southerly latitudes in the Southern Hemisphere.
To see the young moon with Venus and Mercury, you’ll need a crystal-clear sky and an unobstructed horizon in the direction of sunset. A lofty view from balcony or hill will be to your advantage, too. Bring along binoculars, if you have them, and scan for the pale and slender lunar crescent over the sunset point on the horizon, starting about 40 minutes after sunset.
From northerly latitudes on March 18, the moon sets first, followed by Venus and then Mercury. At middle North American latitudes, the moon and Venus set roughly 75 minutes after sunset, whereas Mercury sets about 85 minutes after the sun. At mid-northern latitudes in Europe and Asia on March 18, Venus and Mercury set at about the same time, but the moon will set earlier.
The moon, Venus and Mercury set sooner after sunset at more southerly latitudes. At the equator (0o latitude), Venus and Mercury set about one hour after the sun on March 18; and at temperate latitudes in the Southern Hemisphere, these worlds set about one-half hour after sunset.
Click here for a sky almanac giving you the settings times for the sun, moon and planets in your sky.
Here’s more good news for you young moon seekers in the Northern Hemisphere. We are just a few days shy of the March spring equinox. For the Northern Hemisphere, that means the ecliptic – or path of the sun moon and planets is standing nearly straight up with respect to the evening horizon now.
The steep angle of the ecliptic places the young moon (plus Venus and Mercury) nearly directly above the sunset, as seen from the Northern Hemisphere. Therefore the moon, Venus and Mercury stay for a maximum while after sunset, making these three worlds all the easier to see from northerly latitudes.
What if you’re in the Southern Hemisphere? Because it’s near your autumn equinox right now, the ecliptic hits the horizon at its shallowest angle for the year at sunset. That causes the young moon, Venus and Mercury to set all the sooner after sunset at southerly latitudes.
One last note. Because the ecliptic intersects the horizon at such a steep angle at and around the spring equinox, sky watchers at northerly latitudes now have their best chance to seek out the mysterious zodiacal light some 80 to 120 minutes after sunset. Zodiacal light is interplanetary dust reflecting the light of the sun.
Because this dust circles the sun on nearly the same plane as Earth, watch for this soft, ethereal cone of light to extend upward from the horizon, in the direction of Taurus, a major constellation of the zodiac.
Bottom line: North America has a great shot at seeing the slim young moon, Venus and Mercury in the west after sunset on March 18, 2018. Wherever you are, if you miss the moon tonight, try again tomorrow, on March 19.