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Partial lunar eclipse Thursday

Posted: 24 April 2013

A partial lunar eclipse will occur Thursday, with the best visibility of the brief event in western Australia and South Africa. But observers in the United Kingdom and other parts of the Northern Hemisphere could catch a glimpse with a little planning and luck.

The very slight partial lunar eclipse on 25 April, as seen from Perth. AN graphic by Greg Smye-Rumsby.
The short-duration partial eclipse of the Moon on 25 April, but the Moon only just dips into the Earth's umbral shadow. The magnitude of the eclipse is only 0.0147, which means only 0.5 arcminutes of the Moon's northern limb will be in the umbral shadow.

The eclipse starts with first contact of the penumbral phase at 18:01 UT. The partial eclipse starts at 19:54, with greatest eclipse occurring at 20:07 and the partial phase ending at 20:11. The penumbral phase ends at 22:11. Although times are given for the beginning and end of the penumbral phase, in practice it's impossible to time the detection as there is no obvious edge to the shadow which is clear to see as it moves across the lunar disc. Local sky conditions, lunar altitude, and what degree of optical aid, if any, is employed, will have a great bearing what can be seen. Indeed the whole penumbral phase may go completely undetected and if anything is seen it may be a fair few minutes into the phase before a subtle darkening is seen.

From the UK, the Moon is rising (rises 19:11 UT) as the eclipse is underway and it is only five to eight degrees up. As the Moon pulls further clear of the horizon it might be possible to see the end of the penumbral phase given a dark and transparent sky. The Moon is below the horizon from North America. The whole partial phase is visible from South Africa and the Moon is 50 degrees or so up. The partial phase starts at around 9:50pm local time and is at its greatest at 10:07pm. The event ends around 10:30pm.

In Australia, west is best, with the Moon at a decent altitude of 33 degrees in Perth at the partial phase. The partial eclipse starts in Perth at around 3:48am with greatest extent at 4:07am and ending around 4:30am. With the Moon at a decent altitude, the start of the penumbral phase might be detectable some minutes after 2am. Observers in Adelaide will see the start of the partial phase at around 5:17am with the Moon hanging 15 degrees above the western horizon. Greatest eclipse is at 5:37am and the Moon has sunk to ten degrees by the time the partial phase ends at around 6am.

From Melbourne, the Moon is around 13 degrees up at 5:48am local time for the start of the eclipse and still ten degrees up at 6:07am at greatest eclipse. Those in Sydney have to contend with the Moon only four degree up at greatest eclipse at 6:07am.