There’s an unusual celestial event taking place this week: An eclipse will occur during the moon’s closest pass to earth and a blue supermoon. A lunar eclipse with these variables aligned hasn’t occurred in this part of the world since 1866. (The last blue moon, supermoon, and lunar eclipse actually happened on Dec. 30, 1982, but it wasn’t visible in North America.)
The point in the moon’s orbit at which it is nearest to the earth is called perigee, an event that tends to bring higher tides. This is the second of 14 perigees in 2018. You definitely don’t want to have a coastal storm during perigee — think blizzard of ‘78 conditions.
Why is it called a blood moon?
During a totality in a lunar eclipse, the moon takes on a reddish hue due to light being separated by the earth’s atmosphere before it hits the moon’s surface. The way light waves are scattered by the atmosphere — a process called Rayleigh scattering — also accounts for the colors you see at sunrise and sunset. Depending on the conditions of our atmosphere at the time, the color of the moon can change.
A blue moon is just a another name for the second full moon of the month. We don’t get them very often (hence the phrase “once in a blue moon”). Ethan Sielgell, an astrophysicist who is infinitely smarter than me, has done some of the calculations on exactly how rare this event really is.
He determined that the chance of an eclipse occuring on perigee during a blue moon is about .042 percent, or once every 265 years.
Will I be able to see it?
All of these facts are meaningless if it’s cloudy and we can’t see the eclipse. A coastal storm is forecast to brush the area on Monday and early Tuesday before heading out to sea. This should give us a window of clear skies for the eclipse Wednesday morning.
The moon will be setting during the eclipse along the east coast, which means you won’t see the entire eclipse. As the moon is returning from beneath the earth’s shadow, the moon will have already gone below the horizon.
We will, however, get to see the moon go into totality, which is the coolest part of the eclipse, in my opinion. You’ll need a good view of the western horizon to see this — otherwise trees and buildings will block your view. Since the moon is setting during the event, the higher up you get and can look west, the better the show.
If you do miss the eclipse, don’t worry. You won’t have to wait too long for the next one. A lunar eclipse will be visible locally about a year from now.