Eclipse of the Supermoon.

A total Lunar Eclipse will occur on 28 September 2015, starting at about ten minutes past midnight GMT. It will be visible across much of Western Europe and West Africa, as well as Eastern North America, and all of South America and the islands of the Atlantic and Caribean. Part of the eclipse will be visible from remaining areas of North America, Africa and Europe as well as western Asia and many islands in the Pacific and Indian Oceans, although in these areas the Moon will either rise part way through the eclipse, or set before it is complete.

Areas from which the 28 September 2015 Lunar Eclipse will be visible. In the white area the full extent of the eclipse will be visible, in the shaded areas it will either begin before the Moon rises or end after the Moon has set, while in the darkest area it will not be visible at all. HM Nautical Almanac Office.

The Moon produces no light of its own, but 'shines' with reflected light from the Sun. Thus at Full Moon the Moon is on the opposite side of the Earth to the Sun, and its illuminated side is turned towards us, but at New Moon the Moon is between the Earth and the Sun, so that its illuminated side is turned away from us.

Lunar eclipses occur when the Moon passes through the Earth's shadow. This can only happen at Full Moon (unlike Solar Eclipses, which happen only when the Moon passes between the Earth and the Sum, and therefore only occur at New Moon), but does not happen every Lunar Month as the Sun, Moon and Earth are not in a perfect, unwavering line, but rather both the Earth and the Moon wobble slightly as they orbit their parent bodies, rising above and sinking bellow the plane of the ecliptic (the plane upon which they would all be in line every month).

Because the Moon is passing through a shadow, rather than being blocked from our view, it does not completely disappear during an eclipse like the Sun, but rather goes through two distinct phases of dimming, the Penumbra, when it is still partially illuminated by the Sun, and the Umbra, when the Earth completely blocks direct sunlight from the Moon. This does not result in complete darkness, as the Moon is still partially lit by reflected Earthlight, but it does turn a deep, dark red colour.

Phases of the Lunar Eclipse that will be seen on 28 September 2015. The times are given in GMT, to the nearest 10th of a minute, thus 03.23.5 represents 30 seconds after 3.23 am GMT. HM Nautical Almanac Office.

This lunar eclipse promises to be particularly spectacular, as it occurs on the night of the lunar perigee, i.e. the night when the Moon is closest to the Earth in this lunar month making it appear larger in the sky, with the center of the Moon only 358 876 km from the center of the Earth. The Moon completes one orbit about the Earth every 27.5 days, and like most orbiting bodies, its orbit is not completely circular, but slightly elliptical, so that the distance between the two bodies varies by about 3% over the course of a month. This elliptical orbit is also not completely regular, it periodically elongates then returns to normal, making some perigees closer than others. This September's perigee will be the closest of the year, and the closest since 8 September 2015, when the center of the Moon was only 358 387 km from the Center of the Earth.

Simplified diagram of the Moon's orbit. NASA.

See also...

Partial Solar Eclipse to be visible from Southern Africa, Madagascar and Antarctica on 13 September 2015.

A partial Solar Eclipse will occur on Sunday 13 September 2015, visible from all of Namibia, Botswana, South Africa, Lesotho, Swaziland, Zimbabwe and Reunion Island and parts of Angola, Zambia, Mozambique, Madagascar and Antarctica. The eclipse will occur between 4.41 am and 9.06 am GMT.

The 4 April 2015 Total Lunar Eclipse.

A total Lunar Eclipse will occur on a April 2015, starting at about 9.00 am GMT. It will be visible across much of the Pacific, as well as most of Alaska, the Russian...

Total Solar Eclipse to be visible from Faroe Islands, Svalbard, Friday 20 March 2015.

A total eclipse of the Sun will be visible from the Faroe Islands and Svalbard on Friday 20 March 2015, with a partial eclipse visible from the rest of Europe, West Asia, northern Arabia, North and West Africa, Iceland, Greenland and (briefly) Nova Scotia, Newfoundland and Labrador and parts of eastern Quebec. 

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The Lunar Perigee.

The Moon will be at its closest to the Earth since 19 March 2011 slightly after 9.00 pm GMT on Wednesday 1 January 2014, when it comes to approximately 356 921 km away (in 2011 it reached 356 577 km from the Earth). However this event is unlikely to be observed from the Earth, as this will happen only two hours and fifteen minutes before the New Moon. The Moon completes one orbit about the Earth every 27.5 days, and like most orbiting bodies, its orbit is not completely circular, but slightly elliptical, so that the distance between the two bodies varies by about 3% over the course of a month, with the closest point to the Earth being referred to as the perigee and the furthest point the apogee. This elliptical orbit is also not completely regular, it periodically elongates then returns to normal, making some perigees closer than others. These cycles mean that the Moon will reach its furthest point from the Earth since 2 April 2011 on 16 January 2014, when it reaches 406 536 km away.

Simplified diagram of the Moon's orbit. NASA.

While the 1 January 2014 perigee marks its closest to the Earth in several years, it will not actually be its closest pass of 2014. This will occur on 10 August, when the Moon reaches 356 896 km from the Earth (25 km closer than on 1 January). Similarly the 16 January apogee will not be the furthest from the Earth that the Moon reaches in 2014. This will occur on 13 June, when the Moon will reach 406 568 km from the Earth, 32 km more distant than on 16 January.

See also The December Solstice, Partial eclipse of the Sun to be visible from most of Africa, as well as parts of southern Europe, the Middle East and North and South America, The September Equinox, The Lunar Apogee and The Earth's aphelion.

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The Lunar Perigee.

At 11.11 am GMT on Sunday 23 June 2013, the Moon will be at its closest point to the Earth in 2013, at 356 989 km. 32 minutes later it will officially be full (completely illuminated when seen from Earth), which means the two events will be virtually indistinguishable to human observers, something that has bee dubbed the 'Supermoon' by the popular press. The Moon completes one orbit about the Earth every 27.5 days, and like most orbiting bodies, its orbit is not completely circular, but slightly elliptical, so that the distance between the two bodies varies by about 3% over the course of a month. This elliptical orbit is also not completely regular, it periodically elongates then returns to normal, making some perigees closer than others. These cycles mean that the Moon will reach its furthest point from the Earth (apogee) of the year in the same lunar cycle, 406 491 km at 0.37 am on 7 July 2013.

The moon will appear 16%larger and 30% brighter at perigee than it will at apogee. National Geographic.

While this is being widely hailed as a remarkable event, it is a fairly regular occurrence, and the moon does, periodically, get slightly closer to us than this; it reached 356 953 m on 6 May 2012 (35 m closer) and will be 356 921 m from us on 1 January 2014 (68 m closer). The 1 January perigee will not be the closest of 2014, which will occur on 10 August, when the Moon will reach 356 896 m from the Earth (100 m closer than on 23 June 2013). Thus the closest Moon of 2013 will be exceeded twice in 2014.

See also The Northern Solstice, The March Equinox, Total eclipse of the Sun visible from Australia, Papua New Guinea and the Solomon Islands, 9 May 2013, The Earth approaches its perihelion and The Southern Solstice.

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