PN04/19: Lunar eclipse on 4th May
When the full Moon rises over the UK on the evening of Tuesday 4 May, a total lunar eclipse will already be well under way. The sky will still be bright when the Moon first rises since the Sun does not set until a few minutes later. But as the sky darkens, a dim reddish-brown Moon should be visible (clouds permitting) climbing slowly above the south-east horizon. The total phase of the eclipse will end about 10.08 p.m. BST.
"If the weather is kind to us, this could be a very interesting sight, with the eclipsed Moon becoming more and more obvious as the sky gradually darkens after sunset and the Moon gets higher in the sky," commented Dr Jacqueline Mitton of the Royal Astronomical Society.
Lunar eclipses can only occur at full Moon. They happen when the Sun, Earth and the Moon are in a near perfect line in space and the Moon travels through the long cone-shaped shadow Earth casts in space. The Moon does not become invisible during an eclipse, but appears a dark colour - usually a shade of brown, coppery-red or orange. This is because Earth's shadow is not completely black. Our atmosphere diverts some sunlight, most of it red light, into the shadow. That makes the shadow lighter round its edge than in the middle. The colour the Moon takes on varies from one eclipse to another according to how much dust there happens to be in the atmosphere.
Lunar eclipses are a fascinating and beautiful phenomenon, and no two are quite alike, but they are of no real scientific importance in astronomical research.
High-quality copyright photographs of past lunar eclipses are available from
Contact Fred Espenak via the web site for all uses of these images.
More technical information about this particular eclipse, and eclipses in general, is available from
Date: 27th April 2004
Issued by Jacqueline Mitton, RAS Press Officer.