Driftless Dark Skies: Good Morning (Evening) Earthshine

“I saw the new moon late yestreen/Wi’ the auld moon in her arm”

—Ballad of Sir Patrick Spens

Welcome 2017 with Earthshine! Sunshine and moonshine are probably more familiar. You can easily see how sunshine from our star lights up parts of our moon as it goes through its phases and the dark side wanes and waxes. You can also see how this sunshine is reflected by our moon to light up our darkness here on Earth with moonshine. But there is also sunlight reflected off the Earth, which lights up the dark side of the moon. This is Earthshine, and you can see it best in the days just before and after the new moons on Dec. 29 and Jan. 27.

The show starts on the evening of Dec. 30. Look for a slender moon low in the southwest just after sunset at 4:34 and before moonset at 6:16. On New Year’s Eve, the moon will be a little wider and a little higher in the sky until moonset at 7:15. As the sky darkens at twilight notice how Earthshine lights up the dark side of the moon and lets you make out some of its features. Binoculars make it easier to see the lighter highlands and the darker “seas.”

On Jan. 1, the moon is to the right of Venus bright and brilliant in the southwest. You can enjoy both until moonset at 8:18. On Jan. 2, the crescent moon is between Venus and Mars. Mars is dimmer and ruddier than Venus. On Jan. 3, the alignment changes and the moon is now above and to the left of Mars and Venus. Sunshine now illuminates more of the moon making it more difficult to see the Earthshine. But you can continue to enjoy the moon as it sets later and waxes fuller. On the evenings of Jan. 11 and 12, follow the Full Wolf Moon traveling high in the sky.

Early risers can catch Earthshine just before sunrise later in the month. The Last Quarter Moon is to the left of Jupiter on Jan. 19. Both are visible from midnight until sunrise at 7:28. Keep watching as the moon wanes in size, rises later, and moves closer to the sun. On the morning of Jan. 24, the waning crescent moon is low in the southeast to the left of Saturn. Both are visible from moonrise at 4:33 until sunrise at 7:24. By now, you should start seeing Earthshine again. Look for the even skinnier moon rising in the southeast on Jan. 25 at 5:24. As it rises higher, look for Mercury below it. You’ll want a clear horizon and maybe binoculars for this one.

Don’t miss the grand finale on Jan. 31 as the Crescent Moon, Venus and Mars form a tight triangle in the southwest from sunset at 5:11 until moonset at 9:29. Hope you enjoy beginning 2017 with Earthshine!