Embracing the “Supermoon,” Hyped or Not

Much has been said and written about the Moon's proximity to Earth today. Is that a good thing or a bad thing?

About an hour ago I headed for the studios of WBUR, a terrific public-radio station in Boston, for a live interview on its syndicated "Here and Now" program. H&N's award-winning cohosts, Robin Young and Jeremy Hobson, are both really into what goes on in the skies above, and we often chat about celestial matters arising.

Kelly Beatty at WBUR's Here and Now

S&T Senior Editor Kelly Beatty, at left, chats about the November 14th "supermoon" with Here and Now cohosts Jeremy Hobson and Robin Young at the WBUR studios in Boston.

Yet it was with mixed emotions that I agreed to be on the show. On one hand, we here at Sky & Telescope really don't think today's so-called "supermoon" is that big a deal. Yes, the Moon is closer today than at any time since 1948. And, yes, it's about 8% bigger across and thus 16% bigger in area and brighter than average. And, yes, it's occurring during a full Moon.

In their respective blogs for S&T.com, veteran observers Bob King and Daniel Fischer offered some interesting ideas about perceiving the Moon's swollen orb. Fischer, in particular, believes the larger size can be noticeable.

Yet last night, which was wonderfully clear and even a little balmy by November standards, I looked at the Moon for a long time, intently — knowing that all those geometric rarities were occurring — and I couldn't convince myself that the Moon indeed looked bigger than usual.

Real and "super" Moons

Top: Here's how the not-quite-full Moon looked as it rose last night over Rick Fienberg's observatory in southern New Hampshire. Bottom: And here is Rick's image morphed to show the kind of swollen orb many people think they're going to see during a "supermoon."
Richard Tresch Fienberg

Am I an inexperienced observer? Hardly. Is my eyesight that bad? Hmm.  I asked around the S&T office. Most of my colleagues didn't think the enlargement was obvious, though one or two did. There was some consensus that the Moon looked brighter than usual, if not necessarily bigger. Here's Web Editor Monica Young's take:

"If I hadn't known last night's full Moon was 'super,' I probably wouldn't have noticed any difference when gazing up in a beautifully clear sky last night. I wasn't looking alone, though — and I have media hype to thank for that. The headlines inspired an impromptu star party at my house with a pair of five-year-olds who couldn't have been more excited to look at the Moon through my telescope. They noticed that the Moon was bumpy instead of smooth and that it was covered in circles. (That was before they began running in circles themselves.) Even the two-year-old was clamoring for a look."

And that's the crux of it. We all agree that the term "supermoon" creates artificially high expectations as to what an everyday person is going to see. On the other hand, it's undeniably a plus that lots of folks who wouldn't otherwise give the Moon a second look (or even a first one, for that matter) are heading outdoors to gaze upon the closest full Moon that many of them will likely see in their lifetimes.

. . . though probably not the brightest, due to something called the opposition surge. Right now the Moon is about 5½° south of the ecliptic, so each and every crater shows us a tiny bit of shadow. Were the full Moon right on the ecliptic — as it is just before and after a total lunar eclipse — there'd be no shadows at all and the opposition surge would cause the disk's brightness to jump upward of 20%. (I wish I had measurements to compare the brightness of last night's Moon with the extra-close one that coincided with September 2015's total lunar eclipse.)

But I digress. What do you think about this supermoon stuff? Can you see a difference? Do you care? Drop a comment below to let us know your thoughts.

36 thoughts on “Embracing the “Supermoon,” Hyped or Not

  1. Joshua Hollinger

    Last night I observed the moon for a good 3 hours. I completely agree with this article, the moon didn’t appear any different. I also am experiencing the hype for this super moon. Many people in my neighborhood were stepping out to take a peek at the moon. I do think that it is great to have more people out to see this moon than usual!

  2. Anthony BarreiroAnthony Barreiro

    I took a pair of 15×70 binoculars with home-made neutral-density filters and a tripod up to the top of Bernal Hill in San Francisco yesterday evening to observe the “super Moon” rising over the east bay hills. The weather was mostly clear and moonrise was lovely. After the sky darkened, the moonlight was shimmering on the surface of the bay, which was also quite beautiful. A lot of people were out on the hill to see the super Moon, there was a festive atmosphere (much needed after the recent political catastrophe) and adults and children appreciated the opportunity to look at the Moon through the binoculars. Some people asked questions and I was able to share a bit of information, like “what are those lines coming from that bright circle,” and “why are some parts of the Moon dark while other parts are brighter?” I’m a devoted moonwatcher and to my eye she mostly looked like another full Moon, perhaps a bit brighter than usual, but that was probably just a self-fulfilling expectation. If the hype got people to go out and look at the Moon, no harm done.

    1. Mike-McCabe

      Got to agree, Anthony. No problem with it here either. I was on the opposite side of the continent, Scituate Harbor MA to be exact, must’ve been a thousand people surrounding that harbor and they were there specifically to witness the spectacle of the full moon rising. I had a scope out by the lighthouse and put the eye of anyone who cared to the eyepiece. A surprising number of people asked about a bright spot at 9:00 in the eyepiece (Kepler) and many also inquired about the darker areas (Mare). The weather was beautiful for November here in the NE, people were out and having a good time, and to a person they all thoroughly appreciated the experience of looking through the scope. Oh, and I didn’t experience anyone who had any truly unrealistic ideas about what a “Supermoon” experience would be. In my experience most people get it, and honestly the hype has probably taught millions of people what “apogee” and “perigee” mean. As you said, no harm done.

  3. Bob-PatrickBob-Patrick

    Yes, I did observe a difference as I walked to my car across a shopping center parking lot. A truck driver delivering products to retail store where I work here in Kentucky also noticed a difference and we briefly exchanged our personal comments.

    But what really put the icing on the cake (err, on the Moon) was my wife mentioned the Moon to me and pointed the rising Moon out to me as we waked across our driveway for an evening out.

    And that is quite a difference. Ha! Ha!

  4. Joseph-ShusterJoseph-Shuster

    If the Supermoon hype is good for astronomy outreach, then the Ground Hog Day hype must be great for meteorology outreach.

    The Supermoon frenzy is just the cosmic version of the emperor’s new clothes. Sad that major astronomy outlets, including NASA, are validating the mythology.

    At least the photoshop crowd had a “super” day concocting comically impossible images. (And the public loved them.)

  5. Patrick-McDonald

    I think one problem with the current definition of “Supermoons” is that it allows for several such moons a year.
    We had a presentation at the RASC (Toronto Branch) a couple of years back, in which this suggestion was made:
    “Let’s allow only one “supermoon” a year.
    To qualify, the moment of full moon must be no more than 6 hours away from the moment of perigee.
    This method would eliminate all but 5 of the 13 supermoons between 2014 and 2020
    No year would have more than 1.”

    I am not sure which official Astronomical agency would be best suited to “enforce” such an amended definition, but I believe it would be helpful to do so. Your thoughts on this are welcome. 🙂

  6. Jean LoupJean Loup

    Since my early childhood I have been surrounded by Nature & never ceases to amaze me. “Beauty is in the eye of the beholder” (atributed to Plato) and every Full Moon with unclouded skyes is a spectacle for me. As are those starry nights with New Moons, out of big cities glows. ¿Who cares if it’s “the biggest” ot “the brightest”? It’s the moment we live that’s important, sharing with the Universe.
    Jean Loup.

  7. rs422a

    I’ve been viewing that rock through a telescope for 40 years and I didn’t see any difference with or without the scope. I tried to explain the whole SM thing on Facebook yesterday but they thought I was nuts. Whatever.

  8. Roger

    One of the things that impresses me most about this ‘supermoon’ event is how many folks observed it on the wrong night. The media touted it as November 14th, so everyone went out to look for it Monday night. Full moon was Monday morning at 13:52 UT, or 8:52 AM EST. Perigee was Monday morning at 11:23 UT, or 6:23 AM EST. So Monday morning before sunrise was the time to look! That’s Sunday night.

    You can’t teach the media. You can’t. If they get it right, they accomplish it by luck, not skill.

    1. rs422a

      Preeeecisely. Look, astronomy is just too far out there for the average person. I really like turning people to it by letting them look through my scope. But once they take a glance of something it’s over for them. That’s a little disappointing after seeing their initial reaction to such a magnificent sight. They are bored after that.

      In my mind I’m thinking, “How can you possibly just blow it off like that?”

      I understand how they can and don’t hold it against them, but I cannot blow it off and never will.

  9. Donald BrunsDonald Bruns

    The moon has been in the same orbit for many, many years. Every 29.5 days, it is at perigee. The coincidence is that the moon happened to be full at this perigee. Some of my friends thought that the moon was actually closer this month than it has been since 1948!

    1. Donald BrunsDonald Bruns

      By the way, I actually did image the full moon on the evening of the 13th, a few hours before perigee. But I was taking simulated eclipse data, using the moon instead of the sun, to continue my project to measure the relativistic deflection of starlight during the 2017 eclipse. I have made good progress, and still hope to meet my 1% uncertainty goal.

    2. Kelly BeattyKelly Beatty Post author

      Don: it WAS closer on 14 Nov than it has been, at any time, since 1948. the center-to-center distance was 359,509 km at 11:23 UT. the last time the Moon was this close was 26 Jan 1948, when the center-to-center distance was 356,461.

      1. Donald BrunsDonald Bruns

        Wow, I never realized that the perigee moved in and out by 10’s of km. But is that what made it a supermoon? I thought it was simply because the moon was full when it was pretty close to perigee. (Guide9 has the 1948 and 2016 perigees different by 51km, and the full moons different by 31 km.)

        1. Kelly BeattyKelly Beatty Post author


          I guess if this extra-close perigee had occurred at, say, first quarter then it wouldn’t be considered a supermoon (by astrologer Richard Nolle’s original definition). but, then again, the Sun-Earth perturbations have the greatest effect on lunar distances when the lunar orbit’s long axis points toward the Sun — hence causing the extremes to occur preferentially at new or full Moon.

  10. James-DeCamp

    Apparent magnitude and surface brightness for the two dates in question from NASA/JPL’s website:

    Date__(UT)__HR:MN:SC.fff APmag S-brt Illu% Ang-diam
    2015-Sep-28 02:50:00.000 -12.86 3.39 99.999 2008.331
    2016-Nov-14 13:52:00.000 -12.78 3.47 99.825 2010.352

    It appears Kelly is right. Not a measurement, but an indication. The A difference of 0.08 Magnitudes is a 7.6% difference in brightness. (Surface brightness is “magnitudes per square arcsecond”, but you need to convert to power ratio, not magnitude before summing and convert to magnitude again.


      1. James-DeCamp

        Kelly’s question was how bright? APmag (Apparent magnitude) answers that question. The magnitude indicates how bright something is. Negative magnitude is brighter than positive, the smaller the magnitude the brighter the object is. A change of 1.0 magnitude is a difference of 2.51 times in brightness. (It’s a logarithmic scale, like decibels. Relative magnitude = -2.5 x log10( relative brightness. 10^(1/2.5) ~ 2.51.) The moon during the last lunar eclipse was 0.08 magnitude brighter than the super moon. ( -12.86-(-12.78)). 10^(.08/2.5) = 1.076 or about 7.6%

        S-Brt is surface brightness and is important for astrophotography. Venus has much greater surface brightness than the moon, Jupiter has much less. When computing exposure and ISO settings it’s the starting point. It turns out that the moon in September 2015 also exhibited about 7.6% more surface brightness (0.08 Magnitude more) – probably because it was on the ecliptic, as Kelly pointed out. You can compute magnitude from surface brightness, diameter and percent illuminated. It’s a long story.

        The difference in size (ang-diam – angular diameter in arcseconds) favors the supermoon, of course, but the percent illuminated (in addition to surface brightness) favors the September 2015 moon. The illuminated area would stack up as:

        September 2015: (2008.331)^2 x PI/4 X 99.999/100 = 3167820 sq. arcsec

        Supermoon2016: (2010.352)^2 x PI/4 X 99.825/100 = 3168643 sq. arcsec

        So illuminated area amounts to a 0.00029 magnitude difference in favor of the supermoon, negligible compared to difference in surface brightness in contributing to overall brightness.

  11. Bkellysky

    Looking at the moon Monday at moonrise, I was surprised. I could observe a little more detail than usual with the unaided eye. I snapped a photo with my android camera of my 2 1/2 year old granddaughter with the moon in the background. I swear it looked smaller in the photo than I perceived it to be looking at the same scene with my eyes. I cursed myself for leaving my Canon XS back at the house, since the granddaughter is a big fan of the moon and would have loved to have a nice photo with some lunar details.
    I’ve tried a number of years ago to look at the moon on the horizon with one eye unencumbered and then quickly switching to the other looking through a paper tube. The moon appeared to shrink in size as I switched eyes, a great example of the moon illusion.
    With so much written about it, I think Joe Rao’s article was the best.

  12. Antonio Mario

    While taking my lab out to the yard this past Thursday morning, around sunrise, much to my surprise the waning Moon seemed clearly of an angular size larger than usual. Something like what Bkellysky above experienced. I had to leave quickly for an appointment and decided to take a photo the next morning. Of course it’s been cloudy since.

      1. Bkellysky

        Using bkellysky on the nasaspaceflight.com web site, I was thanked for my great writing. I was feeling pretty good about myself until I saw they liked ‘your S&T articles’, confirming they had mistaken me for Kelly Beatty. 🙂

  13. bwanabwana

    Not too sure if it was any larger or brighter than the dozens of Moons I’ve photographed over the years but it was a hoot having the local camera club on our front deck early in the morning for coffee, a few stories and some great photography opportunities. My album of Super Moon shots at: https://flic.kr/s/aHskLVhGGd

  14. Graham-Wolf

    Hi Kelly

    Liked your photo in the Boston Studios.
    Had similar experiences earlier in the month, on NZ’s Radiolive! National Talkback, re the SuperMoon.
    The media hype seemed (frankly) rather disproportionate to the scientific importance of the event. Told the nation, to simply… “step outside, look up, and enjoy”.
    NO scope needed for this one!

    Down here at 46 South, rained out for several days in a row.. so didn’t get to see it:- this time.

    Then, we had that rather nasty 7.8 shake near central NZ, to deal with, a few days ago. Over 5,000 aftershocks and still counting. Part of the Capital badly trashed, dozens of building still evacuated, others too badly trashed to repair, and are being dropped to the ground. Expect about 20 billion to repair it all, on top of 60 billion to finally repair and rebuild Christchurch… and that was some 6 years ago. National Observatory at Tekapo is completely unscathed, Phew!

    Regards from 46 South, NZ.
    Astronomy is still carrying on, down here!

    Graham W. Wolf.

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