Wednesday, 2 August 2017

Partial Lunar Eclipse, 7 August 2017.

A partial  Lunar Eclipse will occur on Monday 7 August 2017, starting slightly before 3.10 pm GMT. The whole eclipse will be visible across all of East Africa, much of Asia, Indonesia, western and central Australia and the islands of the Indian Ocean, while part of the eclipse will be visible from the remaining areas of Africa, Asia and Australia, as well as Europe, the islands of the Pacific and South Atlantic and the eastern part of Brazil, although in these areas the Moon will either rise part way through the eclipse, or set before it is complete.

 Areas from which the 7 August 2017 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 in a total Lunar Eclipse 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.  In a partial eclipse the Earth passes completely through the Moon's penumbra, but only partly through its umbra.  

 Phases of the Lunar Eclipse that will be seen on 7 March 2017. The times are given in GMT, to the nearest 10th of a minute, thus 17.22.2 represents 12 seconds after 5.22 pm GMT. HM Nautical Almanac Office.

See also...

http://sciencythoughts.blogspot.co.uk/2017/06/the-2017-june-solstice.html
http://sciencythoughts.blogspot.co.uk/2017/07/mars-reaches-solar-conjunction.html

http://sciencythoughts.blogspot.co.uk/2017/05/closest-lunar-perigee-of-2017.html
http://sciencythoughts.blogspot.co.uk/2017/06/saturn-at-opposition.html
http://sciencythoughts.blogspot.co.uk/2017/04/jupiter-at-opposition.html
http://sciencythoughts.blogspot.co.uk/2017/04/uranis-reaches-solar-conjunction.html

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