Why you should look skyward on Saturday night

By Peter Griffin 23/06/2010

If you are out on the town late on Saturday night, hopefully still celebrating the All Whites trashing Paraguay, you may want to head out onto the street to look at the moon.

How the total lunar eclipse in December may appear
How the total lunar eclipse in December may appear

That’s because a partial lunar eclipse will be visible across New Zealand, the South Pacific and part of eastern Australia. A lunar eclipse, according to Wikipedia,  happens when “the moon passes behind the earth such that the earth blocks the sun’s rays from striking the moon”.

Alan Gilmore of the Mt John observatory has more detail:

On Saturday June 26 New Zealand, the South Pacific and the eastern two-thirds of Australia see all of a partial lunar eclipse. The moon begins to enter the penumbra, the fuzzy edge of Earth’s shadow, around 8:56 pm but little change will be seen in the moon’s appearance for an hour. Gradually it will become obvious that the lower edge of the moon is darker than the upper. The darkening will be plain around 10:17 when the moon begins to enter the umbra, the dark central shadow.

The fuzzy bight out of the moon’s lower edge will grow till 11:39 when it will cover more than half the moon’s width. After that it diminishes until the moon leaves the umbra at 1:00 a.m. The shading across the moon will persist for a while as the moon moves out of the penumbra. It leaves the penumbra completely at 2:21 a.m.

In summary: penumbral eclipse begins 8:56 p.m. NZST

Umbral eclipse begins 10:17

Maximum eclipse (0.452) 11:39

Umbral eclipse ends 1:00 a.m.

Penumbral eclipse ends 2:21

So the best time to check out the partial lunar eclipse will be close to midnight. What you’ll see won’t be as impressive as what we may be treated to in December when our region will see the second half of a total lunar eclipse. This could look quite impressive, with the moon expected to have a deep red hue. Says Gilmore:

Most of the North Island will see the moon rise almost fully eclipsed. Only a small part of the upper edge will out of the umbra. By moon-rise in the South Island the moon will be completely eclipsed in the umbra. This is bound to attract a lot of attention.

Maximum eclipse is at 9:17 p.m. NZDT (8:17 UT). The moon begins to leave the umbra at 9:54 and is fully clear by 11:02. It leaves the penumbra at 0:06 a.m.

But it doesn’t end there…

Our luck with lunar eclipses continues into 2011. On the morning of June 16 the moon will set fully eclipsed, as seen from New Zealand. That eclipse begins the penumbral phase at 5:23 a.m. At 6:23 it touches the umbra and is fully immersed by 7:22 when it is setting in northeast NZ. Southerners will see the setting moon at mid eclipse. The moon is likely to be quite dark in colour as it will then be close to the centre of the umbra.

Here are some diagrams from the Royal Astronomical Society of New Zealand that show exactly where the partial lunar eclipse on Saturday night will be visible:


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