Visible in the western United States — including Hawaii —and Australia and Asia in the early hours of January 31, a full moon will turn an orangey-red hue as it passes through the Earth's deep shadow.
That it happens to also be a supermoon and a blue moon makes it a true once-in-a-lifetime event. An all-in-one blue moon, supermoon, and total lunar eclipse has not happened in North America since 1866.
What is a supermoon, a blue moon, and a blood moon?
These are three completely different things that just happen to be occurring simultaneously. A supermoon is when the moon looks slightly bigger than normal, but only by a small margin. It happens because the moon’s orbit around Earth is elliptical, so sometimes it is actually closer. When that coincides with a full moon, it's called a supermoon.
This isn't an extraordinarily infrequent event. There was a supermoon on both December 3, 2017 as well as January 1, 2018. But the full moon on January 31 is particularly special, as it also happens to be a blue moon.
A blue moon isn't a visual spectacle. When there are two full moons within one calendar month, it’s called a blue moon, but it happens rarely. Hence the phrase, "once in a blue moon." The real visual spectacle on January 31 is the blood moon.
What is a total lunar eclipse?
A blood moon is more accurately known as a total lunar eclipse. Astronomers call it an 'umbral eclipse' because the entirety of the moon enters the darkest part of Earth’s shadow, called the umbra. Earth is always projecting a huge shadow into space, but the moon only sometimes passes through it. That can only happen during a full moon, when the Earth is aligned between the sun and moon.
The spectacle begins with what's called a penumbral eclipse, as the moon crosses into the Earth's lighter shadow and causes it to lose its usual brightness. About an hour later, the moon enters the umbra and begins to turn orange or pink on its edge.
About 40 minutes later, the whole of the moon is within the umbra — that's called totality. Unlike during a total solar eclipse, lunar totality lasts for about 40 minutes, during which time the moon is closest to the center of the Earth's shadow. The physics is the same as for a sunset: sunlight is being bent through the Earth's atmosphere before it hits the moon. The exact color depends on Earth's atmosphere, which filters different color spectrums. If there has been any volcanic activity, for example, and there's ash in the atmosphere, a 'blood' moon can result.
Once totality is over, the process reverses, with all color receding as the moon leaves Earth's shadow and returns to full brightness, like nothing unusual has happened.
When is the 2018 supermoon and total lunar eclipse?
This rare celestial event occurs, rather inconveniently, before sunrise on January 31 for observers in North America. Although the partial eclipse begins about an hour before, the all-important totality starts at 12:51 Universal Time, and lasts for one hour 16 minutes. Visit www.timeanddate.com/eclipse and enter your town to see the local times for your precise location.
For those in Australia, New Zealand, Asia, and the Middle East, the eclipsed moon will be visible after sunset on January 31.
What’s the best location to see the 2018 super blue blood moon eclipse?
Anywhere on the night side of Earth, though in North America it’s worth heading west. Those in the east will see only a partial lunar eclipse, and no change in color. Although totality can be glimpsed slightly further east, Denver will be one of the first cities in the United States to see the entire event. Totality begins in Denver at 05:51 a.m. Mountain Standard Time, and ends at 07:07 a.m., just minutes before moon-set. The Rockies, however, could block the view of the latter stages, so further west is best. The timings are identical for Salt Lake City, but moon-set happens 07:41 a.m. local time, so the moon will be higher in the sky.
Those in Los Angeles will enjoy better visibility. Here, totality begins at 04:51 a.m. Pacific Standard Time, and ends at 06:07 a.m. before moon-set at 06:54 a.m. A big, copper-colored moon will be visible close to the horizon.
But it's Honolulu, Hawaii that gets the very best view of the entire event. Totality here starts at 02:51 a.m. Hawaii-Aleutian Standard Time, and ends at 04:07 a.m., with the whole eclipse visible high in the sky long before the moon sets and the sun rises.
How to photograph the super blue blood-moon eclipse
There are two reasons why a total lunar eclipse is the very best time to photograph the moon: not only will it be unusually colored, but the full moon will also be far less bright than usual.
If you want a close-up of the moon you will need to attach a DSLR to a long telephoto lens or a telescope. However, a wide-angle lens can also get great results. Auto-focus on the moon during the early penumbral phase using the LCD screen, then switch to manual focus to lock the shot.
Common settings to try on a DSLR or manual camera are ISO 200, f11 aperture, and exposures of 1/60 second to 1/15 second. When totality begins and the moon takes on color, try three or four-second exposures at ISO 800 or ISO 1600. You’ll probably also capture stars around the moon. MrEclipse.com has additional tips and techniques.
If you don't have a DSLR, try using a smartphone through a small telescope, or through the back of a pair of binoculars.
When is the next super blue blood-moon eclipse?
Over 150 years in the making, don't get your hopes up for another super blue blood-moon eclipse in North America. There’s not long to wait for the next blue moon, however, because two full moons will also occur in March 2018. The next blue blood-moon eclipse will happen on December 21, 2028, though will be only partly visible in this region.
But the real spectacle on January 31 is the total lunar eclipse, which is a surprisingly common event. Visible over a much wider area that a total solar eclipse, the next total lunar eclipse will occur on July 27, 2018 for moon-watchers in South America, Europe, Africa, Asia, and Australia. There’s another one on January 21, 2019 for those in North and South America, the Pacific, Europe, and Africa.