Lunar Eclipse 28 September 2015: The Blood Supermoon

Stargazers in the UK are ideally placed to see a rare astronomical event next week, a Total Lunar Eclipse. While not as dramatic as a Total Solar Eclipse, a lunar eclipse is well worth watching for, as the Moon turns deep red at totality.

A Blood-red Lunar Eclipse

Unlike a Total Solar Eclipse, where totality lasts only a few minutes, a total eclipse of the Moon last several hours. In the morning hours of Monday 28 September the lunar eclipse begins at 0111BST and ends at 0622BST as the Moon sets. During the very early and late hours of the lunar eclipse you will see part of the full Moon’s disk darken, but it’s only when the Moon enters totality that it will turn red. This dramatic event will happen between 0311 and 0423BST.

This month’s lunar eclipse is made even rarer by the fact that the full Moon on 28 Sep is what’s called a Supermoon. This means that the Moon is closer than normal to Earth, and will appear slightly larger and brighter in the sky. But don’t believe the hype: it will be only a few % closer and so your eye will not be able to detect the difference between this Supermoon and any other Full Moon – except this time it’ll be blood red due to the eclipse! (The Moon may actually look bigger to you if you catch it low on the horizon, but that’s due to the Moon Illusion).

The brilliant XKCD sums up the Supermoon hype nicely

A lunar eclipse occurs when the Moon, in its orbit around the Earth, passes into the Earth’s shadow, as cast by the Sun. You might imagine that this would happen once every lunar orbit, or once a month. That it does not is due to the fact that the Moon’s orbit around the Earth is tilted by around 5 degrees compared with the Earth’s orbit around the Sun. So in most orbits the Moon passes above or below the Earth’s shadow.

However, once in a while (there are at least two lunar eclipses each year) the orbital planes will align so that the Moon passes through the Earth’s shadow, sometimes just grazing it, in which case we get a partial lunar eclipse, and at other times passing right through the shadow, when we get a total lunar eclipse.

The Earth’s shadow has two distinct regions, forming two concentric cones: the inner, darker, part of the shadow is called the umbra, and objects within this part of the shadow receive no direct light from the Sun. The outer, lighter, part of the shadow is called the penumbra, and objects within this part of the shadow can receive direct light from the Sun, but part of the Sun’s disk will be obscured by the Earth, and so less light than normal falls on the object.

There are several distinct phases of a lunar eclipse, as the Moon travels through the penumbra and umbra. For this lunar eclipse the total time during which the Moon is at least partially in the Earth’s shadow is 5 hours 11 minutes, and 72 minutes of this is spent entirely within the umbra, i.e. in total eclipse.

These phases are given the names: P1, the time when the Moon’s disk enter the penumbra; U1, the time when the Moon’s disk enters the umbra; U2, the time when the entirety of the Moon’s disk is within the umbra; U3, the last time when the entirety of the Moon’s disk is within the umbra; U4, the last time when part of the Moon’s disk is within the umbra; and P4, the last time when part of the Moon’s disk is within the penumbra.

The UK is ideally placed to view this total lunar eclipse, although you will have to stay up very late, or get up very early. The Moon is in the sky for the entirety of the eclipse. Observers in western Europe, NW Africa, E North America, and South America will all see the full eclipse from beginning to end.

A detailed information sheet for this eclipse (and others) is available (pdf) on the NASA Eclipse website.

Solar Eclipse 20 March 2015

UPDATE: Teachers! Educators! Don’t miss out on the learning opportunity of a lifetime! This partial eclipse will be the best seen in Scotland and much of the UK since 1999, and the best until 2090. And you don’t need eclipse glasses to experience it. 

Indeed, looking at the Sun is a very minor part of the experience. The most incredible thing to happen on Friday morning will be the darkening of the day, as the Sun gets covered by the Moon and much of its light gets blocked out. This will create a dusk-like atmosphere; birds will start singing, insects will come out, flowers – if you can find any – may close up! This is such an unusual and rare event that I really hope every school pupil in the country will get the opportunity to experience it. The best time for this is straight after register (0900) until around 0945.

If you have eclipse glasses you could let some of the pupils use those but I understand that you probably don’t have many pairs and fear the younger children might not use them correctly. Don’t use them then! Just get outside, tell the kids not to look at the Sun, and explore the wonderful daytime darkness. I really hope you can turn this into the learning opportunity of a lifetime.

On the morning of Friday 20 March 2015 there will be a total eclipse of the Sun. Between 0830 and 1042 the Moon will pass across the face of the Sun, blocking out part of its light. The maximum extend of the eclipse will happen at 0934 for a few minutes.

A Total Eclipse of the Sun, visible from the Faroe Islands on 20 March 2015

Unfortunately the “path of totality”, i.e. those parts of the world that will see a total eclipse, is in the far north Atlantic and Arctic oceans. Residents of the Faroe Islands get a ring-side seat at the total eclipse.

Path of Totality, Friday 20 March 2015

That said, it will still be a dramatic event in the UK, south of the path of totality, as we will see a partial solar eclipse where the Moon blocks some but not all of the Sun’s light.

A partial eclipse from Anamosa, Iowa. Credit: Steve Wendl – See more at: http://astrobob.areavoices.com/page/112/#sthash.ElDDdLAg.dpuf

The further north you are in the country the more of the Sun will be obscured, but wherever you are in the UK it’ll look quite dramatic. Here’s a handy table showing what % of the Sun’s disk will be obscured by the Moon from where you are.

Town/City	% Eclipse on 20 March 2015
Lerwick, Shetland	96.8%
Kirkwall, Orkney	96.6%
Inverness	95.6%
Aberdeen	93.9%
Glasgow	93.7%
Edinburgh	93.1%
Belfast	93.0%
Newcastle	90.7%
Liverpool	89.4%
Manchester	89.1%
Birmingham	87.3%
Cardiff	86.7%
London	84.4%

Compare this with the August 1999 eclipse, where totality passed across the SW of England. During that eclipse the further south you were in the UK the better. Indeed the SW of England and the Channel Islands saw a total eclipse.  I was in Glasgow and saw an 82% eclipse. For me, this eclipse will be even better. In fact for anyone north of Liverpool, the 2015 eclipse is better than that in 1999!

Town/City	% Eclipse on 11 August 1999
Lerwick, Shetland	67.9%
Kirkwall, Orkney	68.7%
Inverness	76.8%
Aberdeen	77.6%
Glasgow	82.2%
Edinburgh	81.8%
Belfast	86.8%
Newcastle	84.8%
Liverpool	90.5%
Manchester	90.1%
Birmingham	93.5%
Cardiff	97.2%
London	96.6%

Wherever you are in the UK though it’s worth watching, but BE CAREFUL. Never look at the Sun directly, even when it’s eclipsed. Here are some safety guidelines for viewing eclipses.