Friday morning’s partial lunar eclipse will flirt with with totality, as the longest for more than a century.
If you’re like us, we never miss a chance to catch a lunar eclipse, be it penumbral, partial or total. Lunar eclipses are a great time to catch the surety of the clockwork Universe at its best, as the Moon slides into and then exits the Earth’s shadow.
First the bad news: Friday morning’s eclipse in the early hours of November 19th isn’t completely total. However, the good news is that at its maximum around 9:04 Universal Time (UT)/4:04 AM Eastern Time (EST) the eclipse narrowly misses totality, at 97.5% partial.
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Lunar eclipses occur at Full Moon, when the intersecting node of the Moon’s orbit along the ecliptic plane falls near the Earth’s shadow cast back into space. The Moon’s orbit is tilted about 5 degrees relative to the ecliptic, otherwise, we’d see lunar and solar eclipses every lunation.
Times and Visibility
Most of North America and the Pacific will see the eclipse in its entirety. Eastern North America, South America, the United Kingdom and Scandinavia will see the eclipse in progress at sunrise, while Australia and the Far East will see the eclipse in underway at sunset; only Europe, Africa and the mid-East will sit this one out. The Moon is in the astronomical constellation of Taurus the Bull when the eclipse occurs.
There are also some noteworthy facets of Friday’s eclipse: This is the deepest partial lunar eclipse that misses totality until the 98.65% eclipse on November 20th, 2086, and since the 99.6% eclipse of October 13th, 1856. This week’s eclipse is also the longest partial eclipse of the 21st century at 3 hours, 28 minutes and 23 seconds in duration, the longest since February 18th, 1440 (at 3 hours 28 minutes and 46 seconds) and until February 8th, 2669 (at 3 hours, 30 minutes and 2 seconds), which is also the longest of 5 millennium span of eclipses from 2,000 BC to 3,000 AD.
Here are the key times for Friday’s partial lunar eclipse:
Penumbral begins: 6:02 UT/1:02 AM EST
Umbral begins: 7:19 UT/2:19 AM EST
Mid-Eclipse: 9:04 UT/4:04 AM EST
Umbral ends: 10:47 UT/5:47 AM EST
Penumbral ends: 12:04 UT/7:04 AM EST
Penumbral duration: 6 hours, 1 minute and 29 seconds
Umbral duration: 3 hours, 28 minutes and 23 seconds
Take a good look at the Moon at mid-eclipse Friday morning and ask yourself: does it look total or partial to you? Would you know it was ‘just a deep partial eclipse’ if you didn’t know better? We had a slightly similar situation during the 2015 tetrad of lunar eclipses, with a totality of just under five minutes in duration during the April 4th, 2015 lunar eclipse. Many observers noted that—to their eyes—the outer limb of the Moon never seemed to go completely dark.
Tales of the Saros
This particular eclipse is member 46 of the 72 eclipses in saros series 126. if you saw the brief (22 minutes total) eclipse on November 9th 2003, then you caught the final total eclipse for this saros series, which started all the way back on July 18th, 1228, and spawned its first total lunar eclipse on June 19th, 1769…the eclipses for this series are now partial only from here on out, with a slim penumbral eclipse ending the saros on (mark your calendars) August 19th, 2472 AD.
Astronomer Nicholas Capricornus witnessed a very similar deep partial eclipse on November 6th 1500, during a jubilee year pilgrimage to Rome.
Astronomer Nicolaus Copernicus observed a partial lunar eclipse (the final lunar eclipse of the 15th century) #OnThisDay 1500, while on a jubilee year pilgrimage to Rome. This was a deep partial, very similar to the lunar eclipse this month on the 19th. pic.twitter.com/61JgW4m9QK
— Dave Dickinson (@Astroguyz) November 6, 2021
Observing the Eclipse
Though this eclipse is technically partial, it’s deep enough that we should still catch a ‘blood moon,’ at least on the Moon’s northern limb. Not all lunar eclipses are the same, and can take on anywhere from a bright, saffron-tinged pink appearance, to a dark brick red hue. The Danjon scale is used to describe the appearance of an eclipse during totality, from 4 (bright) to 0 (dark).
The difference to color from one eclipse to the next is the result of two factors: 1). How central the eclipse is through the Earth’s shadow, and 2). how much ash, dust and aerosols are currently suspended in the Earth’s atmosphere to refract reddish sunlight around the rim of the Earth onto the eclipsed Moon. I would expect Friday’s deep partial to appear fairly bright, though the rash of forest fires worldwide in 2020-2021 may add a reddish tint to the Moon’s appearance. Remember, standing on the Earthward side of the Moon Friday morning, you’d see a total or deep partial solar eclipse.
To date, no human has witnessed a solar eclipse from the Moon… yet.
The eclipse also marks the start of the final eclipse season for 2021, book-ended with the remote total solar eclipse across the Antarctic on December 4th. Take heart: 2022 features two total lunar eclipses, including one on May 16th favoring the Americas, Europe and Africa.
Clouded out, or live in the wrong hemisphere? Astronomer Gianluca Masi and the Virtual Telescope Project have you covered, with a webcast featuring the deep partial lunar eclipse starting at 7:00 UT/2:00 AM EST on November 19th:
Weather Prospects Come Eclipse Day
As of writing this, skies for the Contiguous U.S. (CONUS) looks to be a mix of clear to cloudy on Friday morning. We’ll take another look at the situation and update cloud cover prospects the day prior. If skies look iffy, take heart: you don’t need a completely cloud free sky to catch a lunar eclipse… just a good view of the Moon.
We recently wrote a complete guide to imaging lunar eclipses for Astro-Gear Today. Areas where the eclipse occurs at moonset or moonrise will also have an opportunity to capture the eclipsed Moon along with foreground objects near the horizon. The same regions could complete a feat of visual athletics known as a near-selenelion, spying the eclipsed Moon opposite to sunrise or sunset. Also, keep an eye on ISS-transit Finder, to see if you have a nearby opportunity to see the International Space Station transiting the eclipsed Moon. Finally, watch for flashes on the dark limb of the Moon, from possible meteorite strikes. It has happened before: a flash witnessed on the eclipsed Moon on January 21st, 2018 sent astrophotographers scrambling to review their images worldwide. Though it’s an off year, the 2021 Leonid meteors are active this week, with a peak just two days prior to totality on November 17th.
Don’t miss this last lunar eclipse of 2021, and the longest partial eclipse of this century and a one millennium span.
Lead image credit: Last May’s lunar eclipse, across the star-dappled backdrop of Scorpius. Image credit and copyright: Thad Szabo.