Moon Phases

Young moon: can you see one under 24 hours old?

Very thin crescent young moon against lavender sky.
View at EarthSky Community Photos. | Mohamed Mohamed of Tripoli, Libya, captured a young moon on April 24, 2020. Thank you, Mohamed!

New moon – when the moon will be between the Earth and sun – comes about every four weeks. That means the next evening you have an opportunity to spot an exceedingly young moon. By the way, seeing a moon within a day of new phase is very rare. At such times, the moon is still close to the sun along our line of sight. And its lighted portion turns almost entirely away from us. Whether you’ll see a very young moon depends on where you are on Earth’s globe, and on your sky conditions.

Catching a young moon

Gray background with almost invisible threadlike white crescent.
View larger. | We received the photo above from Sarah Nordin. It’s a very unusual photo of an extremely young moon. It was caught only 15 hours, 19 minutes after the instant of new moon, in daylight, on November 8, 2018. Be sure to click in and view it larger to appreciate it. Sarah caught this moon at Telok Kemang Observatory in Port Dickson, Malaysia. Camera: Nikon D300s. Telescope: Takahashi TOA-150. Camera setting: ISO160_1/640s_RAW file. Congratulations, Sarah!

What’s the youngest moon it’s possible to see?

Definitely, it’s rare to see a moon within about 24 hours of the new phase. But it turns out, if you use optical aid, you can see the moon all the way until the moment of new moon. However, always avoid looking directly at the sun!!

On July 8, 2013, a new record was set for the youngest moon ever photographed (see photos on this page). Thierry Legault – shooting from in Elancourt, France – captured the July 2013 moon at the precise instant it was new. Or most nearly between the Earth and sun for this lunar orbit. Legault’s image (below) shows the thinnest of lunar crescents, in full daylight, at 7:14 UTC on July 8, 2013. Legault said on his website:

It is the youngest possible crescent, the age of the moon at this instant being exactly zero. Celestial north is up in the image, as well as the sun. The irregularities and discontinuities are caused by the relief at the edge of the lunar disk (mountains, craters).

Blue background with extremely thin hairlike partial crescent.
Youngest lunar crescent, this photo captured the moon at the precise moment of the new moon, at 7:14 UTC on July 8, 2013. Image by Thierry Legault. Visit his website. Used with permission.
Man standing with telescope looking at sunshade with a hole for viewing the moon in the daytime sky.
Here is Thierry Legault and his setup for capturing the youngest possible moon. See more photos and read more on his website. Used with permission.

Are you likely to see a young moon with your eye alone?

How young a moon you can expect to see with your eye depends on the time of year and on sky conditions. It’s possible to see the youngest moons – the thinnest crescents, nearest the sunset – around the spring equinox.

When Legault captured the image above, the sun and moon were separated only 4.4 degrees. Or about 9 solar diameters on the sky’s dome. It is extremely difficult, and risky, to try to capture the moon at such a time. Because bright sunlight will drown out the sight of our companion world. And there is also a risk of unintentionally glimpsing the sun and thereby damaging your eyesight.

That’s why Legault used a special photographic setup to capture this youngest possible moon. He wrote:

In order to reduce the glare, the images have been taken in close infrared and a pierced screen, placed just in front of the telescope, prevents the sunlight from entering directly in the telescope.

The record for seeing a very young moon

A longstanding, though somewhat doubtful, record for youngest moon seen with the eye is by two British housemaids. They said they saw the moon 14 3/4 hours after new moon in the year 1916.

Stephen James O’Meara achieved a more reliable record in May 1990. When he saw the young crescent with the unaided eye 15 hours and 32 minutes after new moon.

The record for youngest moon spotted with the eye using an optical aid passed to Mohsen Mirsaeed in 2002, who saw the moon 11 hours and 40 minutes after new moon.

Wow!

But Legault’s photograph at the instant of new moon? That record can only be duplicated, not surpassed.

Tips for observing very young moons

Young moons are located some distance east of the sun on the sky’s dome (because the moon always moves eastward in orbit). Young moons appear to our eye as exceedingly slim crescents. And likely illuminated by earthshine, seen low in the western sky for a brief interval after sunset.

No matter where you are, remember to wait until the sun has completely set before scanning the horizon with optical aid! You’ll also need a flat, clear horizon to the west. Start looking shortly after the sun disappears. So, when bright twilight still fills the western sky look for the infant moon that’s barely illuminated!

And, of course, optical aid enhances your young moon possibilities even more.

Extremely thin thread-like crescent moon in orange sky.
View at EarthSky Community Photos. | Radu Anghel captured the thread-like young crescent moon from Bacau, Romania, on October 17, 2020. Radu wrote: “A very young moon, only 20 hours old. Easy and wonderful to spot even with binoculars, 20 min after the sunset.” Thank you, Radu.

Bottom line: Occasionally you get the chance to look for a very young moon, less than 24 hours old. Look just after sunset.

Click here to check out Thierry Legault’s book on astrophotography.

Posted 
April 12, 2021
 in 
Moon Phases

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