Here’s The Scoop On Sunday’s Supermoon Eclipse

The last total lunar eclipse visible across the U.S. occurred on April 15 this year. Sunday's eclipse will be the final of four lunar eclipses spaced about 6 months apart called a tetrad. Credit: Bob King
The last total lunar eclipse visible across the U.S. occurred on April 15 this year (pictured above). Sunday’s eclipse will be the final of a spate of four lunar eclipses spaced about 6 months apart called a tetrad. No special equipment is needed to view an eclipse of the moon, but binoculars help to enhance color and detail. Credit: Bob King

A wonderful event will take place this Sunday, September 27-28. That night skywatchers across the Americas, Europe and Africa will witness a total eclipse of the moon. And here’s the thing. Two things really. Well, OK, three things. First – it happens during convenient evening viewing hours. Second, it’s the Harvest Moon and third, it’s the closest Full Moon of the year.

A total lunar eclipse occurs during a Full Moon when the Sun, Earth and Moon line up exactly in that order. Light from the Sun (white lines) skirts the Earth’s atmosphere, which bends and reddens it. It reaches and reflects off the Moon back toward the Earth and we see a beautifully colored disk during totality. Credit: NASA with additions by the author
A total lunar eclipse occurs during a Full Moon when the Sun, Earth and Moon line up exactly in that order. Light from the Sun (white lines) skirts the Earth’s atmosphere, which both reddens it and bends it into the inner shadow called the umbra. The reddened light reflects off the Moon back toward the Earth and we see a colorful red or orange disk during totality. Credit: NASA with additions by the author

Only rarely does a total lunar eclipse happen during a lunar perigee, the point in the moon’s orbit when it’s closest to Earth. When perigee occurs at or near full moon, we call it a supermoon. Supermoons are bigger and brighter than your average full moon because they’re closer to Earth. Sunday’s moon will be 8% larger than a typical full moon, but you’ll be hard-pressed to tell the difference because there’s no other moon hanging around to compare it to. Still, maybe some of you with an excellent visual recall will detect a size difference.

Diagram showing Earth two-part shadow, the dark umbra, where no direct sunlight shines, and the outer penumbra, where there's a mix of sunshine and shadow. Times shown are Central Daylight. See the table below for times for four different time zones.
Diagram showing Earth’s two-part shadow, the dark umbra, where no direct sunlight shines, and the outer penumbra, where there’s a mix of sunshine and shadow. See the table at the end of this article for eclipse times across all four U.S. mainland time zones. Credit: NASA / F. Espenak

Lunar eclipses happen 2-3 times a year, but a supermoon eclipse is rare. The last one occurred in 1982 and the next won’t happen till 2033. Ready for the best part? Most U.S. observers won’t have to stay up late to watch this one. Partial eclipse, when the Earth’s shadow takes its first bite of moon pie, starts at 8:07 p.m. CDT (9:07 p.m. EDT, 7:07 p.m. MDT and 6:07 p.m. PDT). Total eclipse begins at 9:11 p.m. and ends at 10:23 p.m. That might be enough moon viewing for you. If not, stick around to 11:27 p.m. and you’ll see the moon pass through the partial phases in reverse and emerge in the clear again.

Animation of Sunday night's eclipse showing the passing first through penumbral shadow and then the umbra and back out again. Credit: Tom Ruen
Animation of Sunday night’s eclipse showing the moon passing through Earth’s shadow and out again. Credit: Tom Ruen

Total lunar eclipses last a long time – this one nearly 3 1/2 hours – and are perfectly safe to view throughout. The early times mean even children can stay up to watch. Have the little ones bring out crayons and paper and ask them to draw what they see. Wouldn’t that look nice hanging on your refrigerator?

Eclipses are very casual affairs. Watch as long or short as you like. The moon begins its saunter by first passing through the outer shadow or penumbra. Here, sunlight and shadow are mixed and the shading is too weak to see until about 20 minutes before the partial phases begin.

Map showing where the eclipse is visible. While total solar eclipses can only be seen along a narrow path, total lunar eclipses are visible over an entire half of the planet. Credit: NASA / F. Espenak
Map showing where the eclipse is visible. While total solar eclipses can only be seen along a narrow path, total lunar eclipses are visible over an entire half of the planet. Credit: NASA / F. Espenak

Sunlight passing around the circumference of the Earth gets scattered just like it does at sunrise and sunset; with the blues and greens removed, only the yellows, oranges and reds remain. In the same way a lens or prism bends sunlight, the remaining ruddy rays are bent by the atmosphere into the otherwise dark shadow cast by our planet. There they wait for the moon. When it arrives, they do a masterful job painting it the most amazing shades of warm color imaginable. The depth of color often depends upon the amount of particulate matter, called aerosols, present in the atmosphere. The more, say from a recent large-scale volcanic eruption, the darker the moon.

Simulated view facing southeast around 9 p.m. CDT Sunday night with the moon only minutes before total eclipse. As the moon moves into Earth's shadow, it goes through a series of "phases" until totality. Source: Stellarium
Simulated view facing southeast around 9 p.m. CDT Sunday night with the moon only minutes before total eclipse. As it moves into Earth’s shadow, our satellite goes through a series of “phases” until totality. The “phases” repeat in reverse after totality. Source: Stellarium

Just before, during and after totality are the best parts of a lunar eclipse, when the moon hangs like a fat red apple in a starry sky. Yes, stars. Before and early on in the eclipse, you’ll see few because they’re washed away by strong moonlight. But totality’s another thing. All that stellar goodness returns including the Milky Way, making for a strangely moving transformation.

The only factor we can’t control – and it’s true for all astronomical events – is the weather. Stay in touch with the local forecast or check the National Weather Service site. If you can’t escape the clouds by driving, there’s still hope. You can watch live webcasts of the event here and here. Finally, if you’d like to know how to take pictures of the eclipse, check out my photo tips article.

 

Eclipse Events EDT CDT MDT PDT
Penumbra first visible 8:45 p.m. 7:45 p.m. 6:45 p.m. 5:45 p.m.
Partial eclipse begins 9:07 p.m. 8:07 p.m. 7:07 p.m. 6:07 p.m.
Total eclipse begins 10:11 p.m. 9:11 p.m. 8:11 p.m. 7:11 p.m.
Mid-eclipse 10:48 p.m. 9:48 p.m. 8:48 p.m. 7:48 p.m.
Total eclipse ends 11:23 p.m. 10:23 p.m. 9:23 p.m. 8:23 p.m.
Partial eclipse ends 12:27 a.m. 11:27 p.m. 10:27 p.m. 9:27 p.m.
Penumbra last visible 12:45 a.m. 11:45 p.m. 10:45 p.m. 9:45 p.m.

8 Responses

  1. Troy

    I notice when I let my neighbors look through my scope they’ll often light up a cigarette. Is there a recommended minimum distance to keep smoking away from optical surfaces of telescopes? I was thinking 5 to 10 feet if the wind isn’t blowing. I’m just wondering because I expect to get more interest during the eclipse and I have a strong aversion to cleaning the optics.
    I’m glad your table includes penumbral visible. I was disappointed that I missed that phase in an earlier eclipses in the tetrad.

    1. astrobob

      Hi Troy,
      I doubt one smoker would make a difference unless they puffed directly on the objective or eyepiece. If it were me – and I don’t care for smoking – I’d ask them to not smoke while at or near the telescope. Smoke burns the eyes and makes viewing difficult. Oh, and you might mention that smoking has been clearly linked to vision loss (I’m sure they’ll LOVE hearing that).

  2. Hey Bob, Though it doesn’t have much to do with the “view” of the eclipse per-se, just curious about alignments of things, i.e. moons orbit vs. the earths rotation given that this eclipse is so near equinox time and also the minor standstill. I think I need draw a picture: earth is tilted 23.5 degrees and moons orbit tilted exactly opposite way about 5 degrees, then sun and moon to each side by 90 degrees at the nodes? Makes my head spin! Anyway I bet a tetrad-perigee-equinox-standstill total eclipse is a rare thing indeed. (like that north pole solar eclipse we had).

    1. astrobob

      Hi Peter,
      Even though the moon’s orbit is tilted 5.1 degrees relative to Earth’s orbit, during the eclipse it lies exactly in Earth’s orbital plane, hovering nearly over the equator. I like your title. Allow me to add more: Tetrad-perigee-equinox-standstill-harvest-supermoon total eclipse.

        1. astrobob

          Don,
          No, the directions are correct. They seem odd because many of us saw the eclipse in the eastern sky. Facing east, the north direction is to the upper left.

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