A total lunar eclipse occurs when the moon passes through the Earth's innermost shadow. When this happens, the moon turns rusty orange or deep red in color and is how it earned the nickname of a blood moon eclipse.

The red moon will pair well with Mars, which reaches opposition just before the eclipse and will also appear orange or red in color.

Unlike a solar eclipse, no special equipment or glasses are needed to view a total lunar eclipse, although onlookers will require cloud-free weather.

Friday's lunar eclipse will be particularly special as it is the longest total lunar eclipse of the 21st century.

The total phase of the eclipse will last for an impressive 1 hour and 43 minutes, while the entire eclipse, including the partial phases, will last for over 6 hours.

One reason why this eclipse is lasting so long is because it is occurring when the moon is near apogee, or the point in its orbit when it is farthest away from the Earth, making it appear smaller than normal.

This is sometimes referred to as a 'micromoon,' and is the opposite of the well-known supermoon, or perigee (when the moon is at its closest to Earth).