Night owls in the UK and Ireland will be able to enjoy a total lunar eclipse this month - if the clouds stay away. But you will have to stay up late to see it! The eclipse occurs when the Full Moon glides through the shadow of the Earth in space.
It can actually be seen from much of the world, including Europe, Africa, western Asia, South America and most of North America.
From Britain, the entire event happens in the early hours of February 21st, meaning you will have to wait up on the night of February 20th.
The Moon will travel deep into the Earth's shadow and will turn a deep shade of orange or red - to see how dark or red it actually becomes, we shall have to observe it for ourselves! It could resemble the picture of a total eclipse shown here, right, by Robin Scagell.
The Earth's shadow is actually composed of two cones, one darker one within the other. To understand the geometry of this, visit this webpage. The outer, lighter shadow cast is called the penumbra and is where the Earth blocks some of the Sun's light but not all of it. The darker central shadow is the umbra.
The diagram below, showing times for the eclipse in GMT, is reproduced courtesy of NASA's "Mr Eclipse", Fred Espenak. (Click on the graphic to view it full-size.) Diagrams for other time zones can be found here. Note that the Moon actually moves into the shadow from the right, although the Moon itself will appear to be crossing the sky in the other direction as the Earth rotates.
First contact with the Earth's pale grey outer penumbral shadow occurs at 00:37 UT (37 minutes after midnight GMT), and the Moon is completely enveloped within an hour.
Since the penumbra is faint, all that is likely to be noticed during that period is a slight darkening of the Moon's leading (left-hand) edge. At 01:43 UT the Moon makes first contact with the umbra, i.e. it begins to enter the darkest part of the shadow.
Totality starts at 03:01 UT, when the Moon is completely immersed in the umbra. Given good conditions, the Moon will be visible with the unaided eye because sunlight is refracted by the Earth's atmosphere onto the Moon, giving it a reddish hue. At some eclipses the Moon appears a bright orange at totality, while at others the Moon assumes a rich brown colour.
Totality lasts for 50 minutes, with mid-eclipse at 3.27 UT, making this the deepest eclipse visible from the UK until June 15th, 2011. At 03:51 UT, the Moon's leading edge emerges from the umbra into the relative brightness of the penumbra, ending totality.
During the eclipse the Moon will lie in Leo, close to Regulus and a few degrees away from Saturn. From the UK, the Moon remains fairly high, with an altitude of around 44 degrees at first umbral contact, 33 degrees at mid-totality (03:27 UT) and 18 degrees when it finally leaves the umbra completely (05:09 UT).
Steadily-held binoculars are the best instruments with which to enjoy lunar eclipses. Most viewers prefer to gaze at these events without worrying about recording them, but some enjoy noting the definition of the umbra's edge and the colour of the Moon, along with timing the contact between the umbra and certain prominent lunar features.
If you are keen for a project, try estimating the totally eclipsed Moon's brightness, using binoculars held the wrong way round, by comparing the Moon's small image with a star or planet. Comparison stars include nearby Regulus (mag 1.35) and Saturn (mag 0.2), Procyon (mag 0.38) and Spica (mag 0.98).
The SPA Lunar Section always welcomes reports from members. You can also post your pictures and results, and check those of other observers, on the SPA Forum.
Join Lunar Section Director Peter Grego at www.lunarobservers.com for a live webcast of the total eclipse of the Moon on February 21, from 01:30 to 05:15 UT (if the event is clouded out a real-time computer simulation of the eclipse will be broadcast).
Peter will be using a 200-mm SCT and a Philips ToUcam Pro, and the view will take in the entire lunar disc.
The next total lunar eclipse visible from the UK will not be until December 21st, 2010, but that sets during the event. There won't be another one fully visible until September 28th, 2015!
Total eclipse of the Moon - Feb 20-21, 2008
