Very late Tuesday night (in fact, just before dawn on Wednesday morning) we’re going to have us a super blue blood lunar eclipse. If that sounds peculiar, it’s because it is–and rare. The last one, in fact, happened in 1866. The key facts about the eclipse are these:
- It’s a “blue moon” eclipse. A blue moon isn’t about color; it’s about having more than one full moon within a single month. This happens…once in a blue moon. Most months are several days longer than the Moon’s 29.5-day run around the Earth, so if you get a full Moon in the first couple of days of a month (February being the usual exception) you’ll also get a full Moon in the last few days of the months. This second full Moon in one month is a blue Moon.
- It’s (almost) a supermoon eclipse. A day before the eclipse, the Moon will be at perigee in its orbit; that is, at its closest approach to Earth. This is called a “supermoon.” Although the eclipse occurs a day after lunar perigee, most people say, wotthehell, and call it a supermoon eclipse.
- There’s nothing particularly bloody about this lunar eclipse, compared to other lunar eclipses. (Because the Moon will be close to perigee, the eclipsed Moon will appear larger in the sky.) The Moon will be in Earth’s shadow, and the Earth’s atmosphere scatters the light that passes through the atmosphere, with blue wavelengths scattered more than red wavelengths. This is why most lunar eclipses leave the Moon looking brown or orange. Much depends on how clear and steady the Earth’s atmosphere is at the time of the eclipse. A very occasional eclipse occurs when the atmosphere is unusually calm and clean; such eclipses are very dark, and the Moon almost black. There’s really no reliable way to predict the color of the Earth’s shadow before the eclipse actually happens.
- Alas for Americans, this eclipse will occur while the Moon is setting, just before dawn on 1/31. If you’re on the west coast, you’ll see almost all of it. If you’re on the east coast, you’ll see relatively little. The best view (and this is sheer chance) is over the central Pacific. Alaska, Hawaii, Japan, eastern China, and (most of) Australia are the places to be. Western Europe, most of Africa, and most of South America are pretty much out of luck.
So. When precisely will the eclipse occur? That depends completely on where you are. Your best bet is to look at the timeanddate.com eclipse page, which has a feature that will display local times for the eclipse if you search on a particular city. Look for the search box, titled “Find Eclipses in Your City,” in the right-hand margin of the page. Most cities of reasonable size will be there. If your town is too small for the search box, search for the closest larger town until you find one.
Here’s an example, for Scottsdale AZ. You’ll get local time for the eclipse begin, end, and maximum. The summary below the umbra/penumbra animation will tell you if a particular phase of the eclipse is visible at your location. In Scottsdale, approximately the last 90 minutes occur after the Moon sets, and thus can’t be seen. In Colorado Springs, the last two hours of the eclipse occur after moonset. Make sure you run the animation, which will give you a very clear picture of how the Moon’s disk crosses the umbra and penumbra of the Earth’s shadow.
Carol and I generally wake up at six or a little after, so we’ll either get up half an hour earlier than usual (no big trick for us larks) or just miss the first few minutes of totality. Now, for the owls in my audience, the better path may be to wait until January 21, 2019. That won’t be a supermoon, nor a blue moon, but eclipse visibility will be almost centered over North and South America, which means that anybody in the US will be able to see it in its entirety.
In truth, total lunar eclipses are common (the Moon is small, and the Earth is big) and in my life I’ve seen dozens. I need to emphasize that Wednesday’s eclipse is remarkable not for how it will look but for its flukes of orbital dynamics that coincide only rarely.
Still, lunar eclipses, irrespective of their orbital dynamics, are celebrations of the beautiful and extravagant universe we live in. Take a look, especially if you’ve never seen one before. Compared to a total solar eclipse, it’s long, slow, and almost meditative. Seeing it in a photo or on TV just doesn’t do it justice. Go out there and use your own eyes. You won’t regret it!
