sky-watchers are preparing for the longest lunar eclipse in almost 600 years.
The longest partial lunar eclipse in nearly 600 years will be visible for a lot of people.
The Moon will be almost completely obscured by the shadows as it moves behind the Earth.
The spectacle will be visible in all of North America, as well as parts of South America, Polynesia, Australia and northeast Asia.
Sky-watchers in the areas with a cloud-free view will see a slight dimming of the Moon on Friday as it enters Earth's shadow.
As the moon passes into the umbra, it will appear as if someone has taken a giant bite out of it.
The Moon will be red by the time the eclipse begins at 10:00 am.
The process goes into reverse as the Moon leaves the shadow and travels around the world.
The dramatic red is caused by a phenomenon known as "Rayleigh scattering", where the shorter blue light waves from the Sun are dispersed by particles in the Earth's atmosphere.
Red light waves are easy to pass through.
The moon will appear red during the eclipse if there is more dust or clouds in the atmosphere.
It's as if all the world's sunrises and sunsets are projected onto the Moon.
When the eclipse ends, it will take more than three hours and 28 minutes.
It is the longest partial eclipse since the year 1440, and will not be beaten until the year 2669.
The good news for Moonwatchers is that there will be a longer total lunar eclipse on November 8 next year.
It's even better news that no special equipment is needed, unlike for solar eclipses.
If the weather on Earth plays ball, you can get a decent view of the spectacle with binoculars, telescopes or the naked eye.
2021.
The partial lunar eclipse will be the longest since 1440.
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