NEWS FEBRUARY 2008
LUNAR ECLIPSE 21st FEBRUARY 2008
During the early morning of Thursday 21 st February 2008 there will be an Umbral (total) Lunar Eclipse. Weather permitting it will be well worth seeing. But what is a Lunar Eclipse and how is it different to a solar eclipse like the one on 11 th August 1999 ?
As Earth orbits the Sun and our Moon orbits Earth there are occasions when all three are aligned. Solar eclipses occur when the Moon passes between the Sun and Earth and the Moon casts its shadow across the surface of Earth. Lunar eclipses occur when the Moon passes through the much larger shadow cast by Earth. This type of eclipse is more common than the solar eclipse simply because the shadow of Earth is larger than that of the Moon.
Lunar eclipses always occur at night, because the sunlight is shining on the opposite side of Earth. This produces the shadow through which the Moon will pass. Looking from the night side of Earth the sunlit face of the Moon will always appear as a full Moon during a lunar eclipse. A Lunar Eclipse can be seen from everywhere on the night side of Earth unlike a Solar Eclipse that can only be seen along a narrow path traced out as the Moon's shadow races across the surface of Earth.
As the Moon moves into the Earth's shadow, the shadow will be seen to start moving across the face of the Moon from the left side as viewed from Earth. The edge of the shadow, which is not as sharp as in a solar eclipse, will creep across the Moon until the whole surface is covered. Not all Lunar eclipses are total, a partial eclipse occurs when the Moon only passes through the edge of the Earth's shadow (Penumbra).
When the Moon is inside the Umbra it is not completely dark. Sunlight passing through Earth's atmosphere is refracted on to the Moon and is reddened giving an eerie red glow to the Moon.
Although there will be plenty of time to enjoy the eclipse (if it is clear) it occurs early in the morning between 03:00 and 04:00 so we will either have to set the alarm clock or stay up and watch the whole event. The timetable below shows the full sequence of events starting at about half an hour after midnight and ending just before dawn at about 6:17. Totality will be between 03:00 and 04:00. See Page 2 of the February Beginners Magazine Click Here.
DETAILS OF THIS YEAR'S ECLIPSE
These times refer to the diagram in the previous column.
A 00:35 First contact with penumbra
B 01:43 Contact with umbra
C 03:00 Completely inside umbra
03:26 Mid eclipse
D 03:51 About to leave umbra
E 05:09 Fully out of umbra
F 06:17 Fully out of penumbra
Let us hope for a clear sky like the lunar eclipse of March 2007.