What’s the Thinnest Crescent Moon You Can See?

A slender crescent Moon is a beautiful and inspiring sight. December and January offer several opportunities to see these exceptional slices in the sky.

A Slender Slice

A 24-hour-old Moon cuts a crisp figure at dusk on February 19, 2015. Notice the shading towards the horns of the crescent caused by crater rim and mountain shadows "slicing out" segments of sunlight.
Bob King

When it comes to seeing a young lunar crescent, my personal best is a 21.5-hour-old Moon. That's a far cry from the record, but what a sight. The Moon was fine china, so fragile you might crack it with the slightest touch. Crater shadows took little bites out of the delicate lunar arc, adding to the exquisite view.

This December and in the coming months, we'll have several opportunities to catch youthful crescents at dusk or senior ones at dawn. A few of these will be extremely challenging, others easier but just as remarkable to behold.

A day-old crescent isn't too difficult to see and a worthy goal for the naked-eye observer. The visibility of young (or old) crescents has much to do with the angle the Moon's path makes to the horizon.

The Moon basically follows the ecliptic, the same path traveled by the Sun and planets. From mid-northern latitudes in late summer and fall, the ecliptic tilts upward at a very shallow from the sunset horizon, so thin crescents barely escape the solar glow and are difficult or impossible to see.

From winter through mid-spring, however, the lunar byway tilts upward at an ever-steeper angle from the western horizon, placing the Moon higher up in the sky and offering us a better view. The opposite situation rules at dawn, with summer and fall the best times to seek the waning crescent.

Because the Moon's orbit is tipped relative to the plane of Earth's orbit, it can range up to 5° north or south of the ecliptic. If the crescent occurs around the northern extreme, visibility is improved for mid-northern latitude observers and similarly for southern observers at its southern extreme.

Crescent Ups and Downs

Even though summer and winter crescents have identical elongations from the Sun, as shown in this illustration, the late summer Moon's path more nearly parallels the horizon after sunset, so it's low to begin with and sets early. By late winter, the Moon's steeper path places it more directly above the Sun, bumping up its altitude. Your latitude also factors into the Moon's altitude — the farther north (or south) of the tropics, the lower the crescent Moon's path across the sky. 
Stellarium / Bob King

Essential to seeking young and old crescents is knowing the date of New Moon and time of sunset / sunrise. This month, new Moon occurs at 1:30 a.m. Eastern Standard Time (6:30 UT) December 18th. Because a crescent's age depends on your location, in this article we'll feature its visibility across North American time zones. I ask forgiveness from European and other observers and encourage you to use the listed times of new Moon at the end this article to determine your own best crescents.

New Moon Bookends

The Dec.ember 17th dawn and December 18th dusk crescents will be challenging! These maps show them about 25 minutes before sunrise (left) and about the same time after sunset.
Stellarium

On the December 17th, the morning prior to new Moon, observers in the central and southern U.S. might see a micro-thin waning crescent just 2° to 3° high in the southeastern sky 35 to 20 minutes before sunrise. From the eastern U.S., the Moon would be just 18.5 hours before new phase. From the Central time zone, 17.5 hours; 16.5 from the Western states; and 15.5 from the West Coast. The farther east you live the easier it will be to see the early new Moon. To attempt this tantalizing challenge, you'll need clear, haze-and-cloud-free skies, a completely open view to the southeast, and a pair of binoculars. If you have access to a mountaintop or a tall hill, all the better.

Prefocus the binoculars at infinity on a bright star earlier that night or point them at the planet Jupiter, well up in the southeastern sky in morning twilight. Start your sweeps to the right of the brightest twilight glow (where the Sun will soon rise) to seek the skinny curve of the lunar crescent. Once you've found it, slowly lower the binoculars while focusing your gaze at the Moon's location to see if you can discern it without optical aid.

For a shot at the evening crescent on December 18th, find a location with a view as close to the southwestern horizon as possible and start searching about 20–25 minutes after sundown. Here are the Moon's ages (give or take) depending on where you live — East Coast: 15.5 hours; Central: 16.5 hours; Mountain: 17.5 hours; and West Coast: 18.5 hours.

Shifting gears

When the Moon is near perigee, it appears larger and moves up and away from the Sun faster compared to apogee. December's crescents occur near apogee.
Stellarium / Bob King

During both events, the Moon's distance from the Sun varies from about 7.5° to 8.5°. Research done by Louay J. Fatoohi and his colleagues at the University of Durham (paper here) have shown that when the Moon is fewer than 7.5° from the Sun, it's impossible to see due to atmospheric extinction, physiological factors, and the shrinkage of the crescent's length caused by crater and mountain shadows clipping the ends. In December, the waning crescent will be an easier sight for the eastern half of the country with the evening crescent easier for the western half.

Other factors influencing the Moon's visibility include perigee timing. If the crescent occurs around the time of perigee (closest to the Earth), it will move up and away from the Sun into the evening sky more quickly, enhancing its visibility compared to the more "sluggish" apogee Moon.

The record for the youngest Moon sighted with the naked eye goes to amateur astronomer Steven James O’Meara, who nabbed a 15 hour-32 minute crescent in May 1990. Mohsen G. Mirsaeed of Tehran broke the record for youngest Moon ever seen with optical aid on September 7, 2002. He observed from a mountain site using giant 40×150 binoculars and held a razor slice of crescent in view for one minute. At the time, the Moon was just 11 hours, 40 minutes past new and 7.5° from the Sun.

New Moon crescent

Here is Thierry Legault's near-infrared image of the extremely thin lunar crescent captured at the moment of New Moon on July 8, 2013. Click here for a larger view.

The ultimate record was set on July 8, 2013, by French astrophotographer, Thierry Legault, who photographed the moment of new Moon. The Moon lay just 4.4° south of the Sun at the time, so its extreme northern edge caught enough sunshine to show as a crescent. Only the camera recorded the historical moment as the sky was much too bright to see the Moon even through a telescope.

Keep the following list of exceptionally young Moons handy, so you can try again on other occasions. It's one thing to set a new record for yourself, but in doing so, you'll witness one of the sky's most inspiring sites — a barely-there Moon.

Below is a list of sub-24 hour crescent moons to watch for across North American time zones from mid-northern latitudes (default is 40° N). To help in determining exactly where to look for the evanescent sight in your local landscape, I recommend the Photographer's Ephemeris app for Android and iPhone. You can also create realistic simulations of the Moon's phase and position with a free sky-mapping program like Stellarium.

  • New Moon, January 16, 9:18 p.m. EST (2:18 UT January 17). Excellent evening window 30–40 minutes after sunset on January 17th in the southwestern sky.  The Moon's age East Coast to West Coast will be 20 hours to 24 hours. This is a great chance to spot a sub-24-hour Moon! Don't forget your camera 🙂
  • New Moon, February 15, 4:06 p.m. EST (20:06 UT). No sub-24-hour Moon visible morning or evening.
  • New Moon, March 17, 9:14 a.m. EDT (13:14 UT). No sub-24-hour Moon visible morning or evening.
  • New Moon, April 15, 9:59 p.m. EDT (1:59 UT April 16). The viewing window is 20–30 minutes after sunset on April 16th for the western sky. The Moon's age East Coast to West Coast will be 21.5 hours to 24.5 hours.
  • New Moon, May 15, 7:49 a.m. EDT (11:49 UT). No sub-24 Moon visible morning or evening.

23 thoughts on “What’s the Thinnest Crescent Moon You Can See?

  1. halfastrohalfastro

    My best with binoculars (8×42) is 13 hours and 46 minutes past new from Cassiopeia Observatory in Oracle, Arizona on January 1, 2014. I instantly turned my camera toward it and captured several pictures. https://www.flickr.com/photos/halfastro/albums/72157639298787074

    Universe Today documented our efforts to capture the new Moon that day. https://www.universetoday.com/107700/ultra-thin-young-crescent-moon-sighted-from-u-s-southwest/

    I have tried a few times to capture crescents between 12 and 13 hours but without success so far (most recent attempt had some haze from California fires in the way).

  2. Joe StieberJoe Stieber

    My personal record for a young moon is 20 hr 01 min old one on 03-Feb-2011. I might have sighted it a few minutes earlier and broken the 20-hour barrier, but I was distracted by a dog walker who was curious about what I was doing. My closest-to-new moon that finally broke the 20-hour barrier was an old crescent, 19 hr 08 min before new on 28-Dec-2016. In both cases, they were picked up with binoculars, then seen with unaided eyes and captured in photos. Neither is anywhere near a record, but nevertheless, I enjoy chasing thin crescent moons near new, and they are usually sublimely beautiful. My location, not much higher than sea level in the New Jersey suburbs near Philadelphia, probably isn’t the best location for finding the thinnest crescents, but one plays the hand that’s been dealt.

  3. Mark-Moyer

    Won’t the ease of seeing a new moon be affected by the Sun-Earth-Moon angle at new moon? That is, since the plane of the Moon’s orbit around the Earth is inclined with respect to the plane of the Earth’s orbit around the Sun, doesn’t that mean that sometimes at new moon the angle will be 0 degrees (e.g. when there’s an eclipse) and other times it will much greater (over 5 degrees, if I have it correct). If the moon orbits 360 degrees in ~28 days, that’s ~13 degrees, so if the maximal Sun-Earth-Moon angle at new moon is 5 degrees, then just by having an optimal new moon you’ll effectively get almost 1/2 day of lighting even when at new moon? I’m not at all sure of this, which is why I’m asking.

    As always, I thoroughly enjoyed the article, Bob!

    1. Bob KingBob King Post author

      Hi Mark,

      Thank you and I’m glad you enjoyed the article. The Moon’s 5.1-degree orbital inclination does indeed have an effect on crescent visibility especially around its extremes south or north of the ecliptic. For southern hemisphere skywatchers, a crescent well south of the ecliptic improves visibility just as a crescent at its greatest declination north is easier to spot from mid-northern latitudes. Thank you for pointing this out, and because you did, I added this tidbit to the story to further illuminate the moon’s many “moves” that keep us on our toes.

  4. Graham-Wolf

    Hi Bob

    When I was a full time astronomer at my nation’s Carter National Observatory in the late 1980’s, I frequently promoted chasing thin Lunar Crescents. I did manage to break 15 hrs twice, with 10×50’s,… just. Several of my attempts even made it into the pages of “CASMAG”. Back in the day, they were popularised extensively in “Sky and “Telescope”. Good on you, Bob, for recreating that international interest again. I think the current record is more like 12 to 13 hours, but it’s certainly a tight squeeze.

    Good luck and best wishes to those having a go.

    Graham W. Wolf at 46 South, Dunedin, NZ.

  5. goodricke1

    The visual records must be tinged with some doubt I feel, averted imagination is a powerful tool…. I remember trying for a 15hr sliver in perfect skies & strong binoculars but no luck.

  6. Anthony BarreiroAnthony Barreiro

    Thanks very much Bob for explaining the geometry so clearly.

    Dramatically thin crescent Moons are thrilling to behold. But the Moon is always beautiful, and her changing appearance from day to day and even hour to hour are endlessly fascinating. The waning crescent Moon, 40 hours before new, rose over my neighbor’s roof during dawn this morning, her brilliant crescent cradling glowing earthshine. Took my breath away, even though no heroic effort was required on my part, and I didn’t set any records.

    1. John Borra

      Perhaps I should elaborate. Using the [department-store quality] 7×35 binocular, I could trace roughly 120 degrees of the lunar crescent, which appeared as a fragile, broken and beaded thread scintillating against the bright twilight sky. It was a memorable experience, also inspired by an article in Sky & Telescope.

  7. Jakob

    At 7.38, this morning from the viewing point I use, the Moon was observed with my binoculars(8×40). Very crisp and clear skies made it possible. Merry Christmas to you all

  8. Chris-Schur

    HI Bob,

    My visual record is not too amazing, 19.2 hours but that was in the 10″ at noon. I am bent on tying Thierry’s record of imaging the moon at new. To do this, rather than look through a hole in a board on a ladder as he did, I am making a huge long extension tube for the 10 inch to blacken the interior of the scope and block the sun from getting in the tube. Ill keep you updated!

    Chris Schur

    1. Bob KingBob King Post author

      Hi Chris,

      I’m thrilled you’ve taken on the challenge. Please let me (us!) know how it goes. If anyone can image this, it’s you. Good luck!

  9. SNH

    Hey Bob,
    Thanks for the article on slim crescent moons. They are awesome aren’t they? I truly believe that it’s a rare sight even for amateur astronomers to spot naked-eye crescents less than 24 hours before/after new since it takes dedication. Seeing my first one was just a truly fantastic sight for me. But since I’ve only seen two, I can’t really even describe my emotions as to how seeing one makes me feel yet! My first was in the morning on December 31, 2013 when I saw a 22.25 hours before new moon. My second was in the evening back on January 28 of this year when I saw a 22.5 hours old moon. I was really hoping that I could see the one on the 17th since it was going to be less than 20 hours before new. Sadly, it rained, and I’m still upset even though we needed it since we here in Arkansas are in an extreme drought.
    I will have to try the next one on Jan 16th that you list, even though spotting evening crescents isn’t my forte. I say that because I find it much easier and I have better odds of spotting them in the morning since:
    1) I get to first catch sight of the Moon while it’s at its most visible and the sky is at its darkest.
    2) I get to see it as it’s getting higher instead of being rushed to catch sight of it before it gets too low.
    3) When I stop being able to make it out, I get to record that time instead of when you first spot it in the evening.
    4) Earlier in the night I can use my astronomy programs to find a star that will rise in the same location as the Moon, allowing me to know right where to look when it rises. That is not as easy to do in the evening.
    But I know that the current records are all in the evening sky. I wonder if because it is harder that’s part of the challenge? Guess I never thought of that before. Well, I’m am not changing because I can never hope to set any records with my horizons blocked a degree of treetops!

    Scott

  10. Ali-Ebrahimi SerajiAli-Ebrahimi Seraji

    I’ve seen a lot of crescents since 2003. The tallest crescent of the New Moon was on December 21, 2014, at 11 hours and 41 minutes. Mr. Mohsen G. Mirsaeed also participated in this observation.
    I prepared a table of important observations from 2004 to 2017, which is in the following section.
    https://m.facebook.com/story.php?story_fbid=10213912669628875&id=1173117119
    I love the slim crescent. I shot two crests with a 0.74 and 0.65 percent phase with a camera and a camera.
    https://m.facebook.com/photo.php?fbid=10213912670868906&id=1173117119&set=a.10207064990561178.1073741827.1173117119&source=48

    Or this crescent with a 0.9% phase
    https://m.facebook.com/photo.php?fbid=10213912775991534&id=1173117119&set=rpd.1173117119&source=49

    Best Rigards
    Ali

    1. Bob KingBob King Post author

      Dear Ali,

      Those crescent photos are amazing. The outline is not only a short segment but breaking into pieces. Note: for readers who check out the photo links, click on the “View Larger Image” link on the left side of the page for the best views.

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