This Saturday afternoon, on 10 December, there will be a total eclipse of the Moon. Eclipses of the Moon occur when the Full Moon passes through the cone of shadow cast by the Earth into space. The eclipse first becomes total at 14:06 UT, reaches maximum at 14:32 UT, and ends at 14:57 UT. The partial eclipse ends at 16:18 UT.

Eclipsed Moon on 21st February 2008 by Ian Halsey

Unfortunately, from the UK, the Moon will already have started leaving the umbra (the central, dark part of the Moon’s shadow) well before moonrise, and the observable part of the partial phase will last from moonrise until 16:18 UT.

From London, Moonrise is at 15:51 UT, from Norwich it is at 15:39 UT and from Sheffield at 15:46 UT. Accordingly observers in Eastern parts of the UK will be able to see just the last 30-40 minutes of the partial phase, provided they have a clear, unobstructed north-eastern horizon.

Sadly, from locations further north and west, with moonrise occurring later in the afternoon, most of the partial phase will be over before the Moon rises. Observers should go out at about the time of local Moonrise when, if the sky is clear, the partially-eclipsed Moon may be glimpsed very low down, close to the horizon, in the north-eastern sky.

One never quite knows how dark or how bright a lunar eclipse will be. Everything depends on the conditions in the Earth’s upper atmosphere through which all light falling onto the shadowed Moon has to pass. There have been eclipses when the Moon has been difficult to find even with a telescope, while at other eclipses it has remained bright red or vividly coloured.

This total lunar eclipse takes place at the Moon’s descending node in eastern Taurus, four days after apogee.  The Moon’s orbital trajectory takes it through the southern half of Earth’s umbral shadow. Although the eclipse is not central, the total phase still lasts 51 minutes. Eastern Asia, Indonesia, Australia and Japan are best placed for viewing this eclipse, near midnight and with the Moon at a good altitude above the horizon.

Further information on this eclipse may be found at:
http://eclipse.gsfc.nasa.gov/OH/OH2011.html#LE2011Dec10T