What is a supermoon?
The "supermoon" describes the moon at "perigee", its closest point to the Earth, a distance of about 226,000 miles.
A supermoon appears 14% larger and 30% brighter than the moon at its furthermost point from the Earth.
Total eclipses of supermoons are rare.
What happens during a total lunar eclipse?
The Earth, sun and moon are almost exactly in line and the moon is on the opposite side of the Earth from the sun.
The moon is full and moves into the shadow of the Earth. When this happens it dims dramatically but remains lit by sunlight passing through the Earth's atmosphere.
Why did the moon turn red?
The Earth's atmosphere scatters more blue light, so that the light reaching the lunar surface is predominantly red.
Observers on Earth see a moon that may be brick-coloured, rusty, blood red, or sometimes dark grey depending on the atmospheric conditions.
Why do some regard the event with trepidation?
So-called "blood moons" have traditionally been associated with Earth-shaking events and disasters.
In addition, today's eclipse will be the last in a sequence of four in a row occurring at six monthly intervals, known as a "tetrad".
What is more they have occurred on biblical feast days, making it an extremely unusual "biblical tetrad".
A passage in the Bible's Book of Joel says: "The sun shall be turned into darkness, and the moon into blood, before the great and the terrible day of the Lord comes."
A total solar eclipse blanketed out the sun earlier this year on 20 March.
