A Near-Miss Total Lunar Eclipse – Sky & Telescope


May 2021 lunar eclipse
The partially eclipsed Moon sets behind a dawn-tinged North Sister peak in the Three Sisters Mountains in Oregon during the May 26, 2021, lunar eclipse. Details: Canon SL1, 75-300 mm lens, 1/10 second at f/8, ISO 400.
Alan Gillespie

The deep partial lunar eclipse on the night of November 18–19 should be spectacular. With 97% of the full Beaver Moon in Earth’s shadow at mid-eclipse we’ll witness nearly all the good stuff associated with a total eclipse including the Moon’s radical color change from bone white to tangerine, along with a brief return of the winter Milky Way. The only thing we won’t see is totality. At maximum eclipse, a silvery 0.7 arcminutes of the Moon’s southern limb will extend beyond the umbra. Lucky for us, full Moon occurs 1.7 days before apogee, shrinking the Moon’s apparent size so more of it squeezes inside the umbra than normal.

Lunar eclipse layout
Lunar eclipses occur at full Moon, when the Moon passes directly behind the Earth into its shadow. If the Earth were airless, the Moon would look completely black during a total lunar eclipse. But the atmosphere refracts reddened sunlight grazing the edge of the planet into the Earth’s umbra, coloring the lunar disk during totality. (Not shown to scale.)
Starry Night with additions by Bob King

As is true with all lunar eclipses, half the planet can see one or more aspects of the event — anywhere the Moon is above the horizon. This includes the Americas, northern Europe, eastern Asia, Australia, and the Pacific. Virtually the entire show will be visible across North America. Click here for a coverage map. Two weeks and a half-orbit later on December 4th, the Moon will totally eclipse the Sun from the Southern Ocean and Antarctica.

Impact flash!
Amateur astronomer Christian Fröschlin of the Netherlands captured the flash of a meteoroid impact during the January 20, 2019, total lunar eclipse.
Christian Fröschlin

Coincidentally, the eclipse happens very close to the maximum of the Leonid meteor shower which peaks on November 17–18, raising the possibility of seeing or recording a Leonid meteor impact on the darkened Moon. While it’s an off-year for the shower with a maximum of only about 15 meteors per hour, be alert to the possibility. If you have a second telescope to shoot video for a half-hour or so around mid-eclipse, it may be worth a shot (see, e.g., the Pro-Am Conjunction column in the November issue of Sky & Telescope). Several observers recorded a split-second meteor impact flash during the total eclipse of January 20, 2019.

Eclipse phases by time zone

November 18–19, 2021 AST EST CST MST PST AKST HST
Penumbra first visible? 2:45 a.m. 1:45 a.m. 12:45 a.m. 11:45 p.m. 10:45 p.m. 9:45
p.m.
8:45 p.m.
Partial eclipse begins 3:18
a.m.
2:18 a.m. 1:18 a.m. 12:18 a.m. 11:18 p.m. 10:18 p.m. 9:18
p.m.
Mid-eclipse 5:03 a.m. 4:03 a.m. 3:03 a.m. 2:03 a.m. 1:03 a.m. 12:03 a.m. 11:03 p.m.
Partial eclipse ends 6:47 a.m. 5:47 a.m. 4:47 a.m. 3:47 a.m. 2:47 a.m. 1:47 a.m. 12:47 a.m.
Penumbra last visible? —– 6:35 a.m. 5:35 a.m. 4:35 a.m. 3:35 a.m. 2:35 a.m. 1:35 a.m.

November is often cloudy and cold. For big events like eclipses I keep track of the weather using GOES-East satellite imagery, which provides excellent coverage of the eastern two-thirds of the U.S., southern Canada, and Central America. There’s also a GOES-West version.

When you click either link above it defaults to a visible-wavelength image. For night use you’ll need infrared imagery to see and track clouds. Click the Choose bar drop-down menu and select Channel 7. Clicking anywhere on the map will pop up an enlarged view of that region. When you back-arrow to wide-view mode, controls let you increase image size or create an animated loop to discern trends in cloud movement.

Eclipse photo guide

ISO 800 f/2.8 f/4 f/5.6 f/8
No eclipse —— —— —— 1/4000
Penumbral eclipse —— —— 1/4000 1/2000
Partial eclipse (30% covered) —— 1/4000 1/2000 1/1000
Partial eclipse (60% covered) 1/4000 1/2000 1/1000 1/500
Partial eclipse (90% covered) 1/1000 1/500 1/250 1/125
Total eclipse (bright) 1/15 1/8 1/4 1/2
Total eclipse (dark) 1 sec. 2 sec. 4 sec. 8 sec.
Total eclipse (very dark) 4 sec. 8 sec. 15 sec. 30 sec.
This exposure guide is set for ISO 800, a speed suitable for all aspects of a lunar eclipse. The times will yield well-exposed images of the bright or fully eclipsed Moon, with the darkened portion faintly visible. Increasing times will record more shadow color but overexpose the bright part. Use a tripod for longer exposures.
Bob King

The Weather Network also offers a handy, interactive cloud viewer or you can check the U.S. 7-Day Cloud Cover Forecast. If you can’t escape bad weather, Gianluca Masi will live stream the show on his Virtual Telescope site on November 19th starting at 7:00 UT (2 a.m. EST).

Pleiades and eclipsed moon
The eclipsed Moon and Pleiades cluster will pair up during the eclipse. This map shows them at mid-eclipse (3:03 a.m. CST) when the distance from the southern lunar limb to the cluster’s northern border will be about 6.8°.
Bob King

November’s near-totally eclipsed Moon will accompany the Pleiades, one of the brightest and prettiest star clusters in the heavens. At mid-eclipse, just 6.5° separate the two, making for an excellent picture opportunity. Try photographing the scene when the sky is darkest around mid-eclipse. Almost any lens will do depending on what, if any, foreground you include. I recommend a 100- to 200-mm telephoto to capture a bit more detail. With a full-frame sensor, a 100-mm lens has a field of view of 20.4° × 13.7°; a 200-mm lens, 10.3° × 6.9°.

Lunar Eclipse November 2021 CST
November’s lunar eclipse will be very close to total. Observers across North America should have excellent views of the dimming Moon as it crosses Earth’s two-part shadow. At mid-eclipse, only the Moon’s “little toe” will poke out from the umbra. Times are CST.
Gregg Dinderman, Sky & Telescope

Slipping into shadowland

I plan to share the eclipse with a friend. We’ll be observing with everything we’ve got: naked eyeballs, binoculars, and telescopes. Each offers a unique perspective, and a lunar eclipse is long enough to employ them all. The naked eye works best in experiencing the transformation of the night from harsh moonlight and star-poor skies to dark quietude under the cover of umbral darkness. This has always been one of my favorite aspects of lunar eclipses. Without sunlight the Moon looks small and less substantial, as if robbed of its superpowers.

Umbra at Moon's distance
Earth’s umbra at the Moon’s distance spans about 9,000 kilometers or 2.6°. Given the Moon’s orbital tilt of 5.1° it’s easy to see why eclipses don’t happen every full Moon — crossing the shadow is like hitting a bull’s-eye.
Bob King

Binoculars enhance and intensify the Moon’s color transformation and add a third dimension, giving the ruddy globe the appearance of being suspended among the stars. A telescope clearly shows the shadow’s blurry edge, softened by Earth’s atmosphere, as well as other more subtle colors like smoky yellows, shades of tea, and even pale blue (caused by absorption of red light by the ozone layer). It’s also great fun to watch the major craters succumb in succession to the encroaching shadow. Imagine the scene from the Moon, standing atop Tycho’s central peak watching the Earth slowly cover the Sun. Wow!

Comet Leonard during lunar eclipse
Make a side trip to Comet Leonard when the sky is darkest. The comet lies in Coma Berenices just over the border from Canes Venatici. Stars are plotted to magnitude 10 and north is up.
Stellarium

Consider a side trip to Comet Leonard at mid-eclipse for a special surprise. That morning, the comet will appear about 20′ south-southwest of the 10th-magnitude galaxy NGC 4395 and will glow around magnitude 9. You might even glimpse it in 50-mm binoculars. But not for long! The Moon has places to go and soon enough departs the valley of shadow to flood the sky with light again.

The slow rhythm of a lunar eclipse provides an opportunity to stop, catch our breath, and fall in line with the three most significant cosmic bodies in our life.


To read more on the lunar eclipse and other fun celestial events this month get the November issue.

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