Australia set for total eclipse of moon

IT will be big, round and red, and early tomorrow morning sky watchers across Australia will be treated to a total eclipse of the moon.

Surprisingly, the moon won't vanish as the sun does during a total solar eclipse, thanks to the geometry of Earth, the sun and the moon in relation to one another.

The eclipse begins at 3:25am AEST and enters its darkest phase, totality, at 5:22 am AEST.

It will be possible to see the entire one hour and 41 minutes of totality from each capital city except Brisbane, where the moon sets while totally eclipsed.

During totality the moon should be at its reddest.

"Deep lunar eclipses such as this typically turn a blood-red or even coppery colour, but this is very dependent on the amount of dust and cloud in Earth's atmosphere," explained Andrew Jacob, acting curator of Sydney Observatory.

Particles in the atmosphere scatter blue light, but the red remains.

As the depth of red produced by a total lunar eclipse is an indication of atmospheric conditions, remnants of the ash plume from the Chilean volcano that erupted on June 4 should deepen the colour.

A lunar eclipse takes place when the moon passes through the Earth's shadow, or umbra.

This eclipse will be especially long as the moon will pass precisely through the middle of the Earth's umbra.

Such a perfect alignment of the sun, Earth and moon is called a syzygy, from the Latin word for "conjunction", syzgygia.

Total lunar eclipses don't occur every full moon since the moon's orbit is tilted in relation to the Earth's orbit around the sun.

When it's full the moon usually passes above or below the Earth's umbra.

According to stargazer Dave Reneke, news editor of Sky & Space magazine, astronauts on the moon would see an amazing sight, the Earth eclipsing the sun.

"They'd see a bright red ring around the Earth as they watched all the sunrises and sunsets happening simultaneously around the world."

Night owls who miss tomorrow's eclipse will have a second chance on Saturday December 10, beginning at 11:45 pm.