When To See Ghostly ‘Earthlight’ At Its Best This Week With Naked Eyes

There are few more beautiful and unique sights in all of nature than a slim crescent Moon hanging above the western horizon just after sunset. Having just emerged from the Sun’s glare after its invisible New Moon phase, its slither of light indicates the start of its 29.5-day journey around our planet, but look carefully and you’ll be able to see the dark side of the Moon.

That subtle light on the otherwise unlit lunar surface is called—among other things—“Earthlight”—and it’s the result of sunlight being reflected from the Earth on to the Moon.

This week is a fabulous time to see it at its brightest and best.

With a New Moon on Friday, June 19, a crescent Moon will be visible in the subsequent four evenings (aside from June 20, when it will still be in the Sun’s glare), every time displaying this ghostly light.

It’s only possible to see “Earthlight” when the Moon is a thin crescent, for two reasons:

• Just before, during and just after the New Moon there’s a Full Earth, so our planet’s full glare reflects all of its sunlight on to the lunar surface.
• Our eyes can appreciate the dynamic range between extreme light and dark really well when the Moon is just a crescent, but its growing glare makes that too difficult once the Moon reaches First Quarter and is, from our point of view, 50%-lit by the Sun.

What causes ‘Earthlight’

“Earthlight” is caused by sunlight reflecting off Earth’s oceans and ice. It tends to be brightest between April and June, according to NASA.

Also called “Earthshine,” “Planetshine” and “Da Vinci glow” after the man who first described it in the 15th century, this monthly sight is about to be visible after sunset.

Here’s when to see “Earthlight”:

1. After sunset on Sunday, May 21

Look to the northwestern sky after sunset today and you may be able to see a very slim, 5%-lit crescent Moon very low on the horizon. This will be the most difficult observation of “Earthlight” of the whole week, but also likely the most rewarding.

Above it you’ll see the very bright planet Venus and, beyond that, a much less bright Mars.

This is what it will look like:

2. After sunset on Monday, May 22

Look towards the northwestern sky after sunset tonight and you’ll see an 11%-lit crescent Moon just below Venus among the stars of Gemini. The “Earthlight” will be impossible to miss in a clear sky.

This is what it will look like:

3. After sunset on Tuesday, May 23

Tonight an 18%-lit crescent Moon will be visible between Venus and Mars with Gemini’s brightest star, Pollux, very close to the Moon. By now the “Earthlight” will be spectacular, but by tomorrow it will begin to fade as it gets overpowered by the growing and ever-brightening crescent.

This is what it will look like:

How to see ‘Earthlight’

Look at the Moon with your naked eyes and you’ll see “Earthlight” quite easily if the sky is clear. However, point any pair of binoculars—whatever size you can get your hands on—at the Moon’s darkened limb for a great close-up of its craters bathed in the eerie light.

Wishing you clear skies and wide eyes.