The Partial Lunar Eclipse of 2010, June 26

A lunar eclipse is different from a solar eclipse in the relative positions of the three celestial bodies namely the earth, moon and the sun. Whereas a solar eclipse is caused by the interruption of the sun’s view from the earth, it is the reverse in the case of a lunar eclipse. During a lunar eclipse the earth is positioned in between the sun and moon along the same line such that the light of the sun is either fully or partially blocked from illuminating the moon. What we are seeing is celestial game of light and shadows since the earth and moon do not generate light but reflect the suns rays.

Before you can understand the concept of a lunar eclipse, let me explain the two terms: umbra and penumbra. These refer to the shadows produced by celestial bodies when the source of light is another celestial body and hence is not concentrated at a point. This leads to the shadow of the intervening body to be as shown in figure 1 below. The dark colored region is the umbra while the other is penumbra. There is another region called antumbra but we will not discuss here for sake of simplicity.

Now look at the above diagram again and imagine that the light source is the sun and the shadow object is the earth. If the moon lies behind the earth on or near an imaginary line connecting the sun and earth, it will be in the region of umbra or penumbra shadow. Depending on one's location on earth, the lunar eclipse could either be partial eclipse, total eclipse or penumbral eclipse. It must be remembered that from the standpoint of an average person it is only the first two which are visible, the third should be left for the astronomers to gaze at, because the shadow of the earth in the penumbral region is not strong enough to cause a change in the illumination of the moon, which is easily visible to the naked eye.

After reading about lunar eclipses you might be wondering when the next eclipse is? Well, one eclipse just passed on the last day of 2009, the 31^st December, but obviously most people would be busy welcoming the New Year with loud music rather than watching the silent sight in the night sky. The next partial eclipse occurs on the 26th June 2010 and if you want a detailed list of the dates of lunar eclipses, just click here.

Just because the lunar eclipse occurring on 26^th of June 2010 is partial, that does not mean that you should totally ignore it. So try to observe whatever changes you can in the illumination of the moon and compare it with the total eclipse later on. Viewing the eclipse with a pair of binoculars makes for a great view, as you can follow Earth's shadow as it moves across the lunar surface.

In the meantime, you can enjoy a lunar eclipse by viewing the pictures below till the real drama in sky begins. You can see the figure 1 below to find out more details regarding that. The various parts of the globe have been differentiated based on color to describe the regions in terms of the visibility of the eclipse. If you are worried that the eclipse is not visible at much parts of the land, you can try using the sea route for viewing the same by taking a cruise trip.

The picture (figure 2) after the "Areas of Lunar Eclipse" image shows the time lapse photography of a lunar eclipse which has already occurred in the past. That should give you a good idea of how the lunar eclipse looks over a period of time. Just remember that this picture is of total lunar eclipse while the one on the 26th June 2010 is a partial lunar eclipse.

Figure 1: NASA Website

Figure 2: Lunar Eclipse in the Background of Eiffel Tower