MILLIONS of stargazers watched Saturday night's "blood moon" in the shortest lunar eclipse this century.

A partial eclipse was visible across Australia, although views along the east coast were hampered by bad weather.

Saturday night's eclipse was the shortest of the century, with US-based Sky and Telescope magazine describing it as "unusually brief".

This was the third lunar eclipse in a series of four, known as a tetrad.

The first two were in April and September last year, with the final eclipse in the cycle on September 28 this year.

For a lunar eclipse to occur, the sun, earth and moon must align roughly in a straight line.

Even though the earth completely blocks sunlight from directly reaching the surface of the moon, it's still visible to the naked eye.

The earth's atmosphere refracts sunlight which lights up the moon's surface, but the atmosphere removes certain elements of the light spectrum, giving it the red colouring.