You might – or might not – catch the young whisker-thin moon below the planets Jupiter and Saturn after sunset December 15. The frail waxing crescent moon will be sitting low in the sky, and close to the sunset point on the horizon. Shortly thereafter – most likely before nightfall – the moon will be following the sun beneath the horizon. On December 15, you may need binoculars to tease out the lunar crescent from glow of evening twilight.
Live in the United States or Canada? Click on Old Farmer’s Almanac to find out the moon’s setting time in your sky.
Given clear skies, it’ll be easier to see the moon each day after December 15 for three reasons:
A greater portion of the lunar disk will be illuminated by sunlight.
The moon will be higher up in the sky at sunset.
The moon will stay out longer after sundown.
Think photo opportunity on December 15 and 16, as the lunar crescent moves into the neighborhood of the two largest planets in the solar system, Jupiter and Saturn. Jupiter is the larger and brighter of these two brilliant beauties, outshining Saturn by 11 times. So if you see Jupiter and not Saturn, aim binoculars at Jupiter to see both Jupiter and Saturn taking stage in the same binocular field of view.
While the moon is joining up with Jupiter and Saturn at dusk and early evening, look for the soft glow of earthshine to adorn the dark side of the moon. Earthshine is twice-reflected sunlight: first from the Earth to the moon, and then from the moon back to Earth. When the moon is slender crescent in Earth’s sky, our planet is an almost-full waning gibbous Earth in the moon’s sky. Thus, our big, bright Earth lights up the dark or nighttime side of the crescent moon.
By the way, in a week or so – on December 21, 2020 – the planets Jupiter and Saturn will showcase their closest conjunction since July 16, 1623. A conjunction of Jupiter and Saturn is often called a great conjunction, which only recur in periods of 20 years. A similarly close Jupiter-Saturn conjunction won’t happen again for another 60 years, until March 15, 2080.
Jupiter-Saturn conjunctions from 2000 to 2100 inclusive:
May 31, 2000
December 21, 2020
November 5, 2040
April 10, 2060
March 15, 2080
September 24, 2100
For a big challenge, try catching the young moon shortly after sunset on December 15. Thereafter, watch for a wider – yet still slender – lunar crescent to join up with the close-knit planets, Jupiter and Saturn.