When it comes to Lunar eclipses, you can have three types. The total eclipse, with the characteristic red blood color the Moon takes, happens when the lunar surface is completely within the shadow of the Earth. The partial eclipse is where only portions of the Moon are covered by our planet's shadow. And then there is the penumbral eclipse when the Moon crosses the penumbra cast by Earth. The penumbra is the "almost shadow" of our planet.
A penumbral eclipse is happening on May 5, 2023, and it will be visible everywhere on Earth apart from the Americas and a bit of the North-West of Europe. The best view will be for people in Australia, China, Japan, those around the Indian Ocean, and South East Asia. That’s about 83 percent of the world’s population. But what are you actually seeing during a penumbral eclipse?
The Moon, over the course of a couple of hours, will become dimmer as 96.4 percent of the surface of our natural satellite passes through the penumbra. This is not a full shadow (umbra) so the Moon will not become darker. Celestial objects are not always perfectly aligned during eclipses, so it is possible for eclipsing bodies (in this case the Earth) to only partially cover the Sun. If you were on the surface of the Moon, you’d be seeing the Earth’s disk covering part of the Sun but not all of it.
Here on Earth, the Moon will appear dimmer but the effect is not as stark as when the actual shadow covers the Moon. The best time to see the effect is when the eclipse is well underway, with one area being brighter than the rest.
The eclipse will last for four hours 17 minutes and 31 seconds. It starts at 3:14 pm UTC and the moon will be almost completely in the penumbra around 5:22 pm. This is the last of four lunar eclipses of the Metonic cycle that happen on the same date, around May 5, every 19 years.
The next lunar eclipse will be a partial one on October 28. The next penumbral eclipse will be on March 25, 2024, and will be visible almost exclusively from the Americas, as if to make up for those peeps who won’t be able to see this one.