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Get ready for the total lunar eclipse!

Total lunar eclipse

We'll all get to see a total eclipse of the Moon on the night of December 10/11, 2011.

  • Total lunar eclipse, Saturday, December 10
  • Visible from all over Australia and New Zealand
  • Easy to see — you don’t need a telescope

SKYWATCHERS in Australia and New Zealand will be treated to a total eclipse of the Moon, late in the evening on December 10 and into December 11.

An eclipse of the Moon happens when the Moon moves into the Earth’s shadow. If the Moon goes through the middle of the shadow, it is a total lunar eclipse. (If it “cuts the corner” of the shadow, we get a partial eclipse.)

There are usually 2-3 lunar eclipses each year, but they’re not always visible from the same place. From any particular spot on Earth, you might see 1 or 2 per year.

December 10 lunar eclipse

There are two parts to the Earth’s shadow—the outer, dim penumbra; and the inner, darker, umbra. When the Moon moves into the penumbra it is, technically, in eclipse, but it is very hard to see any darkening of the lunar surface. Some eclipses occur only in the penumbra, and the darkening is so slight that most people wouldn’t even know it was happening.

For this eclipse, the Moon will start to move into the umbra at 11:46pm, Australian Eastern Daylight Time (AEDT) on Saturday, December 10. That’s 8:46pm in Perth, 11:16pm in Adelaide and 9:46pm in Darwin.

This won’t be a very long event compared to others that we’ve seen recently. The Moon will be fully eclipsed for only 51 minutes (but there are the partial phases before and after).

But unlike some eclipses where particular areas miss out on seeing the start or finish, everyone will be able to see the whole thing from end to end (weather permitting of course).

Mid-eclipse will occur at 01:32am AEDT, and the whole thing will be over by 3:18am AEDT on Sunday morning. (Adjust for your own time zone.)

Diagram of eclipse

The stages of the eclipse. U1 is where the Moon starts to move into the darkest part of Earth's shadow (the umbra) and where the first "bite" appears to be taken out of the lunar disc. U2 is where the Moon is fully inside the shadow and is therefore totally eclipsed. U3 is where the Moon begins to move out of the umbra, and U4 is where it is fully out of the umbra.

When and where to see it

The Moon will be in the northern part of the sky. As long as the weather is clear, you won’t have any difficulty seeing the eclipse.

You won’t need a telescope or binoculars – just your own eyes are enough to take in the view.

And it’s good to remember that eclipses happen fairly slowly, so if you don’t fancy staying out to watch the whole thing, just go outside every 10-15 minutes or so and see how it has changed.

And of course, unlike solar eclipses, lunar eclipses are perfectly safe to watch.

Eclipses in 2012

Next year will be a thin one for eclipses for Aussies — there’ll be one, pretty average partial lunar eclipse, but we’ll get a fantastic total eclipse of the Sun.

The partial lunar eclipse will occur on June 4, 2012, and will be visible from eastern and central Australia.

The total eclipse of the Sun will occur on the morning of Nov 14, 2012—and it will be the last one to be seen in Australia until the year 2028! Totality will be seen only along a narrow swathe of far north Queensland near Cairns. Everyone else will see a partial eclipse.

Here are some more web resources for the December 10 total lunar eclipse:

Melbourne Planetarium’s Skynotes site

IceInSpace guide to the eclipse

Royal Astronomical Society of New Zealand guide to the eclipse

Wikipedia page on the eclipse

Story by Jonathan Nally. Many thanks to Tanya Hill, astronomer at the Melbourne Planetarium, for spotting an error in the original timings given above; now corrected.

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