A total lunar eclipse will be visible across the United States and other parts of the Western Hemisphere Thursday evening or Friday morning, depending on the time zone.
Also known as a “blood moon,” the eclipse will cross the San Antonio night sky between midnight and 4 a.m.
A “blood moon” occurs when the Earth’s shadow — as the Earth moves between the sun and the moon — covers the moon entirely. The passing of light through the Earth’s atmosphere filters through a reddish hue that colors the satellite.
Angela Speck, professor and chair of the physics and astronomy department at the University of Texas at San Antonio, described the hue as “every sunset and sunrise reflected at the moon.” It is a nice way to think about it, she said.
This March full moon is referred to as a “worm moon.” This name originated from Native American tribes in portions of northeastern United States, who observed earthworm casts in the ground as snow and ice thawed at the end of winter.
Total lunar eclipses happen about twice a year, but only one hemisphere of the Earth can see it each time because of the Earth’s rotation, Speck said.
San Antonio skies will see 25% cloud coverage early Friday morning, said Cory Van Pelt, meteorologist for the National Weather Service. Temperatures will range between 60 and 70 degrees, with winds of 5-7 mph.
The eclipse will last approximately six hours. In comparison, solar eclipses only last a maximum of 7.5 minutes. Speck said lunar eclipses take longer as the moon moves through the Earth’s larger shadow, which is about four times larger than the moon.
“When it starts, you can see like a bite being taken out of the moon,” Speck said. “It’s bright enough that you can see it.”
Although visible to the naked eye, NASA recommends zooming devices like binoculars or telescopes improve the viewing experience.
The moon will go through five stages during the eclipse, starting with moon beginning to enter the Earth’s shadow and ending when the moon has exited Earth’s shadow.
‘Blood moon’ stages
March 13
- 10:57 p.m. — The penumbral eclipse begins, when the moon begins entering the Earth’s shadow. The shadowing is dim.
March 14
- 12:09 a.m. — Start of partial eclipse. This is when the moon begins to visibly darken.
- 1:29-2:31 a.m. — Totality of eclipse. The moon is completely shaded during this time.
- 3:47 a.m. — End of partial eclipse. This is when visible shadow has gone past the moon.
- 5:00 a.m. — End of penumbral eclipse. The moon has exited Earth’s shadow.
This is the only eclipse, lunar or solar, that will be visible from San Antonio in 2025.
Speck said she recommends San Antonians seek darker environments by getting away from city lights. Staying away from streetlights as much as possible is recommended if one can’t make it out.
Unlike in a solar eclipse, when protective glasses are needed against the intense sunlight that can damage eyesight, eclipse glasses are not needed to see the “blood moon” phenomenon.
