NASA | Lunar Eclipse Essentials
"Lunar eclipse expected to turn the moon red"
Skywatchers anticipate spectacular lunar elipse tonight as the moon will rise in the Earth's shadow
June 15th, 2011
The moon will rise in Earth's shadow this evening in a rare lunar eclipse that could turn our natural satellite a deep shade of red.
With clear skies, the celestial spectacle will be visible across the UK, with the exception of northern Scotland, as soon as the moon rises after sunset.
Moonrise time varies with location, but for observers in London, the show will begin at 9.13pm. Further north, in Glasgow, moonrise begins at 9.58pm.
A total lunar eclipse happens when the moon, Earth and sun line up, and our home planet casts a vast shadow that engulfs the moon.
When the moon moves into the darkest part of the Earth's shadow, the umbra, it will turn a slate grey or brick red colour.
The moon changes colour because blue light - and other short wavelengths - scatter more in the Earth's atmosphere, with more red light getting through.
The Royal Astronomical Society said the eclipse, if visible, could be a spectacular opportunity for photographers. The moon will remain low in the night sky, so observers will need a clear horizon and cloudless skies to see it well. Unlike solar eclipses, a lunar eclipse is safe to watch with the naked eye.
The event will be visible in Australasia, southern Japan, a large area of Asia, India, Africa, Europe and the eastern part of South America.
The total eclipse ends at 22.03pm, when the Moon starts to leave the darkest part of the umbra. At this time, the moon will be only five degrees above the south-eastern horizon from London, whilst in Glasgow the whole of the lunar disk will not yet have appeared and from northern Scotland it will not be visible at all.
In the final stage of the eclipse, the moon moves into the lighter part of Earth's shadow, the penumbra, and will likely take on a yellowish hue. The eclipse will be over just after midnight, at 00.02am Thursday morning.
Check Space Weather for amateur photographs.
YouTube will be broadcasting on the Web a red-glowing lunar eclipse today at 11:20 a.m. PDT that otherwise will only be visible in the skies of South America, Africa, Asia, Australia and Europe. Sorry, North America.
The lunar event will last about 100 minutes and be live-streamed in video to Google's official YouTube channel.
"We're always fascinated by the unique wonders of space and the world -- what can we say, it's the geek in us," wrote Noel Gorelick, Google's chief extraterrestrial observer, in a company blog post.
"Naturally, when we learned that part of the world will be treated to a rare 100-minute-long total lunar eclipse starting at 11:20 am PDT today, we were both excited and disappointed that this rare occasion wouldn't be visible from our Mountain View campus like last year's eclipse."
Suspecting they weren't alone in wanting to see the eclipse, a team of Googlers contacted the folks at Web-broadcasting Slooh SpaceCamera to get a real-time video feed of the eclipse onto YouTube.
Slooh is hosting a mission interface Web app, built using Google's App Engine technology, that will also broadcast the video feed and will be "equipped with audio narrations from real-life astronomers so you can hear a firsthand, expert account of the event," Gorelick said.
"If you're fortunate enough to be able to view this event in the sky, we hope you'll get the chance to step outside and indulge in the spectacle," Gorelick said. "For everyone else, we hope our moon madness helps brighten your day."
The eclipse will be the first full eclipse of 2011 and, at 100 minutes, will also be the longest lunar eclipse in more than a decade, according to Spaceweather.com.
The expected red tint will be due to exhaust from the erupting volcano in Chile, which could alter the appearance of the eclipse, Spaceweather.com reported.