Posts Tagged ‘Lunar Eclipse’

Did you catch the lunar eclipse

7 July, 2009

A lunar eclipse happened this evening, beginning at moonrise during dusk over Australia on July 7, and setting over western North and South America in their early predawn hours of July 7.

However, the lunar eclipse only entered the southern most tip of the penumbral shadow, making it extremely difficult to observe visually.

Image: Tom Ruen

(See the diagram… The shadow barely nudges the Moon, and not even the umbral shadow.)

Unlike this somewhat unspectacular lunar eclipse, the total eclipse happening later this month promises to be the most dramatic one in our lifetime, partly because it will be the longest one this century.

If you are in India, China or parts of Japan, you may be in luck to catch the total eclipse.

If you are in the majority of the world not within the eclipse’s path, don’t fret. You can still view it “live” and in real time right here.

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Lunar eclipse time lapse video

26 June, 2009

Still about lunar eclipses, this time lapse video of the 20 February 2008 total lunar eclipse shows what the previous post was referring to about the red Moon. Notice how the Moon totally darkens, then the refracted light from Earth hits the Moon and turns it red.

Red moon of a lunar eclipse

26 June, 2009

Total lunar eclipse (Photo: Fred Espenak, www.MrEclipse.com)

A break from solar eclipses, here’s a amazing picture of a lunae eclipse.

Unlike a total eclipse of the Sun, the Moon during a total lunar eclipse does not completely disappear as it passes through the umbra of the earth’s shadow. This is because of the refraction of sunlight by the Earth’s atmosphere into the cone of the shadow.

This renders the Moon a red colour because sunlight reaching the Moon first passes through the Earth’s atmosphere and becomes scattered.

The short wavelengths are more likely to be scattered by the atmosphere and the particles in it. As such, longer wavelengths (the reds) dominate and continue to pass through. The resulting light we perceive is thus red.

It’s the same effect that causes sunsets and sunrises to turn the sky red. (If we were on the Moon watching the Earth, the Sun would appear to be setting/rising behind the Earth.)

The next partial eclipse of the Moon will occur on December 31, 2009. To see the next total eclipse of the Moon, you will have to wait until December 21, 2010. In the meantime, there’s the chart below which projects its path and appearance.

21 Dec 2010 (Photo: SockPuppet for TomRuen

Comparing a Solar Eclipse to a Lunar Eclipse

7 June, 2009

Pictures help explain things better so here are two diagrams below to demonstrate how a solar eclipse compares to a lunar eclipse. Hope things are clear as day after this.

Solar Eclipse

Solar Eclipse

Lunar Eclipse

Lunar Eclipse

What are Lunar Eclipses then?

6 June, 2009

The Sun isn’t the only object in the sky that gets eclipsed. The Moon can experience an eclipse too.

A solar eclipse occurs when the Moon passes between the Sun and the Earth, blocking the Sun from our view.

Photo: Tom RuenA lunar eclipse occurs when the Moon passes behind the Earth such that the planet blocks the Sun’s rays from striking the Moon. This happens when the Sun, Earth and Moon are aligned with the Earth in the middle.

Since the Moon doesn’t produce its own light, and that what we see in the nightsky is really the Moon reflecting light from the Sun, as it passes behind the Earth and into its shadow, the Moon becomes dark.

There are different types of lunar eclipses. Before we begin, the shadow of the Earth can be divided into two distinctive parts: the umbra and the penumbra. Within the umbra, there is no direct solar radiation. However, as a result of the Sun’s large angular size, solar illumination is only partially blocked in the outer portion of the Earth’s shadow, which is given the name penumbra.

  • penumbral eclipse occurs when the Moon passes through the Earth’s penumbra. The penumbra causes a subtle darkening of the Moon’s surface. A special type of penumbral eclipse is a total penumbral eclipse, during which the Moon lies exclusively within the Earth’s penumbra. Total penumbral eclipses are rare, and when these occur, that portion of the Moon which is closest to the umbra can appear somewhat darker than the rest of the Moon.
  • partial lunar eclipse occurs when only a portion of the Moon enters the umbra.

Author: Tom Ruen

  • When the Moon travels completely into the Earth’s umbra, one observes a total lunar eclipse. The Moon’s speed through the shadow is about one kilometer per second and totality may last up to nearly 107 minutes. Nevertheless, the total time between the Moon’s first and last contact with the shadow is much longer, and could last up to 3.8 hours. The relative distance of the Moon from the Earth at the time of an eclipse can affect the eclipse’s duration. In particular, when the Moon is near its apogee, the farthest point from the Earth in its orbit, its orbital speed is the slowest. The diameter of the umbra does not decrease much with distance. Thus, a totally-eclipsed Moon occurring near apogee will lengthen the duration of totality.