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

[BAA electronic bulletins service]

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:

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
email: docjohn at dircon.co.uk

51 Orchard Way, Barnham, West Sussex PO22 0HX