It's a full moon tonight, but not just any old full moon. This is a very special one. I'm setting my alarm clock to go off at 2:45 am because I want to see tonight's total lunar eclipse.
The moon goes around the earth once a month but its orbit is tilted, so most months it doesn't pass directly through the earth's shadow. But at least twice a year, during a full moon, some part of it will be within the earth's shadow and that's a partial lunar eclipse. Tonight we will have a total lunar eclipse which means the moon will be completely within the earth's shadow for fifty minutes.
If the earth had no atmosphere, the moon would appear black during a total lunar eclipse. But the atmosphere scatters the sunlight, so some light reaches the moon even during totality. However the moon will distinctly darken and change colour. Often it appears reddish. Some eclipses are darker than others, depending on the amount of dust in the atmosphere.
Tonight's total eclipse lasts from 03:01 am to 03:51 am GMT. It will be visible from all of North and South America, and most of Africa and Europe (including all of Britain and Ireland). The next total lunar eclipse will be on December 21st 2010 but it won't be visible from Britain. The next total lunar eclipse visible from Britain will be in 2015, seven years away, which is why I'm getting up at such a ridiculous hour to see this one.
Isn't the photo amazing? It's a multiple exposure photograph of a total eclipse in 2004, taken over Hayward, California. Click on the photo for more information, and to see its license information.