Residents of the Americas, much of Europe and West Africa will be able to observe a total lunar eclipse on the night of January 20 to 21, the last before 2022.
For Europeans and Africans, the total eclipse will occur at the end of the night, shortly before sunrise. The east of these continents will see less because of the rising of the day.
For North and South Americans, it will be early or mid-night.
The full Moon will be in the shadow of the Earth from 3:34 to 06:51 GMT. During the first hour, she will be gently "eaten" by the left. The eclipse will be total for one hour from 04H41 GMT, according to the time tables provided by NASA.
The total phase of the eclipse will be about three quarters of an hour shorter than that of the great eclipse of July 2018, which will remain the longest of the twenty-first century.
During the total eclipse, the Moon will not be invisible: it will be red, as in all total eclipses.
This hue will be due to the fact that the sun's rays will not reach it directly. Instead, a small part of the red rays will be filtered by the earth's atmosphere and refracted towards the Moon (the blue rays will diverge to the outside).
It is the same phenomenon that colors in red the sunrises and sunsets seen from the Earth.
"This is the last chance before a long time to see a total lunar eclipse," says AFP Bruce Betts, chief scientist of the Planetary Society, an American astronomical organization.
The next total eclipse visible from Europe will take place on May 16, 2022, but partial eclipses will occur in the meantime.
Total lunar eclipses can happen two or three times a year.
They correspond to a rare combination of circumstances: the Earth must be exactly between the Sun and the Moon.
It is still necessary that the sky is cleared to enjoy. Clouds often spoil the show.
Astronomy enthusiasts will be able to compare the tiny variations of the red hue of the Moon this time. "It all depends on what's in the atmosphere," says Bruce Betts. "Just as sunsets change color from one day to another, eclipses vary according to the particles in the atmosphere, or if there is a volcanic eruption, for example".
No telescope is needed to observe the eclipse. To see the craters of the Moon, the planetologist recalls that a simple pair of binoculars can do the trick.