Wednesday’s Mercury-Moon Challenge

Observers in North America have a rare opportunity to observe an extremely thin crescent Moon paired with Mercury very low in the west shortly after sunset on Wednesday, February 22, 2012.

Just 30 minutes after sunset. Bring binoculars!
The Moon will be just 24 hours old in Nova Scotia, and 28 hours old on the West Coast. This is nowhere near a record young Moon, but it's a lot younger and thinner than most people have ever observed. Seeing such a faint pencil line in the sky is a startling experience.

You need three things for this sighting: clear air, a site with a completely unobstructed western horizon, and binoculars. The binoculars aren't strictly necessary; in good conditions both Mercury and the Moon should be visible to the unaided eye. But they're a huge help for spotting the pair.

Go out at or immediately after sunset, and start scanning the sky 5° to 10° (one or two binocular fields of view) above the spot where the Sun disappeared. It's forecast to be cloudy in my area, so I won't have a chance, but I practiced up yesterday (Monday) spotting Mercury.

I first caught Mercury in binoculars 12 minutes after sunset, but I couldn't spot it naked-eye until 25 minutes after sunset. It remained just barely visible for the next 10 minutes, by which point is was quite low in the sky. On Thursday Mercury will be 1.5° higher, which may not sound like much. But it should make the observation much easier.

I'm curious whether Mercury or the Moon will be easier to see. The Moon will be 40 times brighter, but its light will be spread over a much bigger area. Please let me know how it looks to you.

In Europe and Western Asia, this will indeed be close to a record-young Moon -- something made possible by the fact that the Moon will be almost directly above the Sun. For detailed information, see the Islamic Crescents' Observation Project website. Months in the Islamic calendar traditionally begin when the young Moon is actually sighted, so Islamic astronomers are the world's experts in predicting its visibility.

If you miss this Moon, it will still be remarkably thin — and much easier to spot — on Thursday evening.

See also my 5-minute TV program on this event, or watch the 3-minute version on You Tube below.

9 thoughts on “Wednesday’s Mercury-Moon Challenge

  1. Tony Flanders

    Colonel Bob Jones asks: "What about those of us in the Southern Hemisphere?" It’s a good question. The answer is that just as conditions are ideally good in the Northern Hemisphere, they’re ideally poor south of the equator. The ecliptic is very steep in the north and very shallow in the south, so Mercury and the Moon are below the horizon a half-hour after sunset at mid-southern latitudes.

  2. Mandy

    Do you submit podcasts on iTunes? If so, what can I search to find them?

    Thanks for the info- I’m excited to check it out tomorrow evening! You’re awesome!

  3. dwm

    Dear Mr. Flanders,

    Thank you for your excellent discussion. I can’t wait to look for the young crescent moon and Mercury after sunset over the Pacific this evening.

    You may be interested in the connections to myth regarding the motion of Jupiter vis-a-vis Venus, and Venus vis-a-vis Mercury. I discussed some here:

    I believe that such myths (along with other evidence of many sorts) constitute evidence supporting the arguments that ancient observers had a very sophisticated understanding of celestial events (including the subtle motion of precession, thousands of years before it was supposedly first discovered by Hipparchus).

    Your video is very nicely done. Armed with that knowledge and direction you have passed along in it, I have high hopes of locating the very young crescent moon and Mercury (as long as there isn’t too much fog!)

    best regards,

    David Mathisen

  4. Don Staka

    Thanks much for this! (and for excellent news). The cloudy sky in CT cleared up at sunset and Mercury was just barely naked eye visible from 6-6:30 EST but easy in my 8×56 binos. A nice yellowish-orange color. The crescent moon was not visible until about 6:15 – never saw it such before. Beautiful evening.

  5. Joe Stieber

    I was able to spot the thin crescent moon at 5:58 pm EST, 15 minutes after sunset at my location in New Jersey (40.0 deg N, 75.0 deg W). I used an 80 mm refractor on a photo tripod with a 40 mm eyepiece (12x, 5 deg field). As soon as I found the crescent, I swung left and saw Mercury. Two minutes later (6:00 pm), I was able to find both of them with my 10×42 binoculars, and at 6:02 pm, I was able to glimpse the moon naked-eye. Even though Mercury was as easy to see as the thin crescent moon in the scope and the binoculars, I was never able to spot it naked-eye. Anyway, the moon was 24 hr 23 min old when first spotted this evening, a few hours older than my modest personal record of 20 hr 01 min, but even so, it’s an incredible sight to behold. Thanks to Tony for broadcasting an alert so that more folks have an opportunity to see this amazing sight!

  6. Margrit McIntosh

    Tucson AZ, local sunset is at 6:15 p.m. and that’s when I started watching. I was out with my binoculars, there were some light wispy cirrus and cirrostratus clouds but I didn’t think they’d be a problem and they weren’t, just enhanced the sunset. Saw Venus first, then Jupiter, and then higher up than I expected I spotted Mercury with the binoculars. I dropped the binoculars and suddenly saw the moon with the naked eye! This was at 6:30. Beautiful! Left horn higher than the right, there was a bright patch in the crescent near the right horn, followed by a dark patch. I could see Mercury with the naked eye 5 minutes later. The moon had still not set when I left the scene at about 6:50. Thanks for the article, it was a wonderfully peaceful end to what was a jangly day at work for me!

  7. Margrit McIntosh

    Also worth noting: my horizon was far from clear, featuring the Tucson Mountains, to say nothing of palm trees, cell phone towers, and the buildings of the medical center, but the moon was still quite high above my visible horizon. Thanks again!

  8. stephen Reisinger

    Feb 22,2012 – Fort Wayne, IN. Rain and Clouds. Darn. The best I have done at seeing the Moon was 27 1/2 hours new. I Observed this at Bear Branch Nature Center, Westminster, MD. Viewed on April 4, 2005 at 8:05 EDT.

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