[BAA-ebulletin 00587] TOTAL LUNAR ECLIPSE THIS WEDNESDAY EVENING

[Rick]

[BAA-ebulletin 00587]  TOTAL LUNAR ECLIPSE THIS WEDNESDAY EVENING
(c) 2011 British Astronomical Association -- http://www.britastro.org/

BAA e-bulletin, 2011 June 11
TOTAL LUNAR ECLIPSE THIS WEDNESDAY EVENING

This coming Wednesday evening, on 15 June, there will be a total eclipse of the Moon. From southern parts of the UK, the Moon will rise totally eclipsed, and the majority of the second half of the total phase will be visible, provided observers have a clear, unobstructed south-eastern horizon. Sadly, from locations further north, with moonrise occurring later in the evening, most of the total phase will be over before the Moon rises; those in northern Scotland will miss totality entirely. Indeed, observers throughout Europe will miss the early stages of the eclipse because they occur before moonrise.

The Moon first enters the outer, penumbral part of the Earth's shadow at 17:25 UT, and the partial eclipse begins at 18:23 UT.  The eclipse first becomes total at 19:23 UT, reaches maximum at 20:13 UT, and ends at 21:03 UT.  The partial eclipse ends at 22:02 UT and the penumbral phase at 23:01 UT.

NOTE:
You will need to add an hour to all UT times given in this e-bulletin to obtain BST.

The entire eclipse will be visible from locations in southern, central and eastern Africa, the Middle East and India. This is the first lunar eclipse of 2011, and it occurs at the Moon's ascending node in southern Ophiuchus. As the Moon passes rather deeply through the Earth's umbral shadow on this occasion, the total phase will last 100 minutes. The last lunar eclipse to exceed this duration was in June 2000.

Further information on this eclipse may be found at: http://eclipse.gsfc.nasa.gov/OH/OH2011.html#LE2011Jun15T

From southern parts of the British Isles, the Moon will rise totally eclipsed and the later umbral phases will be visible as twilight falls. From such locations, the Moon will be very low in the south-eastern sky, close to the horizon but in a gradually darkening sky. From London, the Moon rises at the time of greatest eclipse (20:13 UT), and only from places in the extreme south-eastern parts of England does the Moon rise before this time.

The table below lists the times of moonrise for various locations in the British Isles:

Code Select Expand

Location                  Moonrise (UT)

Whitstable                 20:07
Brighton                   20:09
London                     20:13
Southampton                20:15
Cambridge                  20:16
Bristol                    20:23
Plymouth                   20:24
Birmingham                 20:26
Swansea                    20:29
York                       20:31
Liverpool                  20:36
Newcastle-on-Tyne          20:40
Dublin                     20:49
Edinburgh                  20:54
Belfast                    20:56
Glasgow                    20:58
Aberdeen                   20:59

From the UK, the observable part of the umbral phase will last from moonrise until 22:02 UT. During totality, the Moon will pass slightly to the north of the centre of the Earth's umbral shadow, so the northern parts of the totally eclipsed Moon will most likely appear rather brighter than the southern part. Indeed, the low brightness of the totally eclipsed Moon, coupled with its low elevation above the horizon, will likely make the Moon very difficult to discern at, and for a time after, moonrise. The Moon will be best located using binoculars or a wide-field telescope at this time.  As the Moon rises higher in the sky it will become easier to see, but even from locations in south-eastern England there will be, at most, only about 50 minutes between moonrise and the end of the total phase.

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.

For observers in the British Isles, the very low elevation of the Moon during the total phase means that it is not possible to predict the exact brightness distribution in the umbra, so observers are encouraged to estimate the brightness using the Danjon scale at different times during totality. Note that it may also be necessary to assign different Danjon values to different portions of the Moon (i.e., north vs. south).

For an explanation of the Danjon scale of lunar eclipse brightness visit: http://eclipse.gsfc.nasa.gov/OH/OHres/Danjon.html

The 2011 June 15 total lunar eclipse is the 34th member of Saros 130, a series of 71 eclipses in the following sequence: 8 penumbral, 20 partial, 14 total, 22 partial, and 7 penumbral lunar eclipses.

There will be a second lunar eclipse in 2011, on 10 December, but on this occasion the Moon will have already started leaving the umbra before moonrise.

The BAA Lunar Section will be pleased to receive observations of the lunar eclipse.  See the Section's webpage at http://www.baalunarsection.org.uk/ for more details.


John Mason
BAA Press and Publicity Officer