On November 19, 2021 (late evening of the 18th in a long time zones), the Moon passes into the shadow of the Earth, creating a partial lunar eclipse so deep that it can fairly be called practically overall. Credit: NASAs Scientific Visualization Studio
What is an “nearly total” lunar eclipse?
A lunar eclipse occurs when the Sun, Earth, and Moon align so that the Moon passes into Earths shadow. In a total lunar eclipse, the whole Moon falls within the darkest part of Earths shadow, called the umbra. In this eclipse, as much as 99.1% of the Moons disk will be within Earths umbra.
How can I observe the eclipse?
The best watching will be best around the peak of the eclipse, on November 19th at 9:03 UTC/4:03 AM EDT/1:03 AM PDT. This part of the eclipse shows up in all of North America, in addition to big parts of South America, Polynesia, eastern Australia, and northeastern Asia.
A world map showing where the eclipse shows up at the time of biggest eclipse. Earlier parts of the eclipse are noticeable farther east, while later times show up farther west. Credit: NASAs Scientific Visualization Studio
What can I expect to observe?
All times are in UTC on November 19, 2021.
Penumbral eclipse begins
The Moon enters the Earths penumbra, the outer part of the shadow. The Moon begins to dim, however the result is rather subtle.
Partial eclipse starts
The Moon begins to enter Earths umbra and the partial eclipse begins. To the naked eye, as the Moon moves into the umbra, it looks like a bite is being secured of the lunar disk. The part of the Moon inside the umbra will appear really dark.
Red color becomes visible
More than 95% of the Moons disk remains in the umbra and the Moon will appear red. The color may be much easier to see in binoculars or a telescope. Using a video camera on a tripod with direct exposures of several seconds will draw out the color, at the expense of overexposing the lit part of the Moon.
The peak of the eclipse happens at 9:03 UTC. This is the finest time to see the red color.
Red color no longer visible
The soreness fades as less than 95% of the Moon is in the Earths umbra. It appears that a bite is taken out of the opposite side of the Moon from previously.
Partial eclipse ends
The entire Moon remains in Earths penumbra, however once again, the dimming is subtle.
Penumbral eclipse ends
The eclipse is over.
What else can I see tonight?
Throughout the eclipse, the Moon moves through the western part of the constellation Taurus. The Pleiades star cluster is to the upper right, and the Hyades cluster– including the brilliant star Aldebaran, eye of the bull– is in the lower left. Here are some more skywatching tips for the month of November.
Why does the Moon turn red throughout a lunar eclipse?
The same phenomenon that makes our sky blue and our sundowns red triggers the Moon to turn red during a lunar eclipse. Its called Rayleigh scattering. Light travels in waves, and different colors of light have various physical residential or commercial properties. Blue light has a much shorter wavelength and is scattered more quickly by particles in Earths environment than red light, which has a longer wavelength. Red light, on the other hand, takes a trip more straight through the atmosphere. When the Sun is overhead, we see blue light throughout the sky. When the Sun is setting, sunlight must pass through more atmosphere and travel farther prior to reaching our eyes. The blue light from the Sun scatters away, and longer-wavelength red, orange, and yellow light travel through.
The landscape of the Moon, foreground, is reddened by sunlight filtered through Earths environment. The Sun is obscured by the Earth, but the glow of its corona shows up. Credit: NASAs Scientific Visualization Studio
Throughout a lunar eclipse, the Moon reddens since the only sunlight reaching the Moon travels through Earths environment. The more dust or clouds in Earths environment throughout the eclipse, the redder the Moon will appear. Its as if all the worlds sundowns and sunrises are predicted onto the Moon.
A lunar eclipse takes place when the Sun, Earth, and Moon align so that the Moon passes into Earths shadow. In an overall lunar eclipse, the entire Moon falls within the darkest part of Earths shadow, called the umbra. The Moon starts to get in Earths umbra and the partial eclipse starts. More than 95% of the Moons disk is in the umbra and the Moon will appear red. During a lunar eclipse, the Moon turns red because the only sunlight reaching the Moon passes through Earths atmosphere.