Lunar eclipse, April 4, 2015

Eclipse photo courtesy maarjaara under CC.

Eclipse photo courtesy maarjaara under CC.

AMATEUR ASTRONOMERS and recreational stargazers across Australia will be hoping the weather gods are kind to them tonight, so that they can witness what will be the shortest total eclipse of the Moon of the 21st century.

A lunar eclipse happens when the Moon – slowly moving in its orbit around the Earth – goes into the Earth’s shadow. Sometimes it goes through merely the outside, fainter part of the shadow (the penumbra), and we get only a partial eclipse. But if it goes right through the middle (the umbra), it will be a total lunar eclipse (with partial phases before and after totality).

For a typical lunar eclipse, totality – when the Moon is completed immersed in Earth’s shadow – can last for an hour or more. But for tonight’s eclipse it will be only about five minutes long. (Although some experts are suggesting between seven and 12 minutes; for all sorts of reasons, it’s an inexact science.) That’s because the Moon will only just cut into the deeper part of the shadow.

In fact, this will be the shortest lunar totality for almost 500 years – you have to go all the way back to 1529, when there was a total eclipse of the Moon where totality lasted for a little less than two minutes.

With longer total lunar eclipses, the Moon tends to go a red colour instead of completely black. This is because even though the bulk of the Sun’s light is blocked by the Earth, some wavelengths manage sneak through our atmosphere and get bent, or refracted, onto the Moon.

But that probably won’t happen with tonight’s eclipse, as it will all be over and done with too quickly.

When and where to see it

The great thing about lunar eclipses is that they can be seen from anywhere on the side of the Earth that’s facing the Moon at the time – unlike a solar eclipse, where you have to be in exactly the right spot to see it.

So weather permitting, everyone in eastern and central Australia will be able to see the whole thing tonight from start to finish. For those in WA, the Moon will still be below the horizon as the initial partial phase begins, but it will soon rise and will be nice and high in the sky by the time totality occurs.

Here are the timings for the capital cities (including daylight savings where applicable):

When to see the eclipse

When to see the eclipse

How to watch it

The other great thing about a lunar eclipse is that it is perfectly safe to watch it (unlike a solar eclipse) and you don’t need any fancy gear – your own eyeballs are quite sufficient. However, if you do have a pair of binoculars or a small telescope, take a look and compare the parts of the Moon that are in shadow with the parts that are not.

This will be the only eclipse for Australia this year. So if you have clear skies, make sure you go out and take in this natural spectacle while you have the chance.

Filed Under: AstronomyAustralian ScienceFeatured storiesNight Sky

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