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3 July 2011

Ast. (P) #3: Lunar Eclipse 2011


This is a compilation of photos taken from my digital camera showing in a time lapse of 7 minutes and the phases of the shadowing of moon observed from the living room in my house, convenient much! especially totality (full eclipse of moon) occurred around 3.25am local time. Because the photos are taken without any magnification, the image we see is in fact a small cut-out, enlarged from a relatively high pixel camera. (from my DSLR). This leads to the badly resolved grains seen in the images.

Lunar eclipse occur when the sun, earth and moon are perfectly arranged in a straight line where the earth is in the middle, therefore lunar eclipse can only occur in the night of full moon. The length of lunar eclipse is much longer than solar eclipse is because of the relative size of the moon compared to earth. Think about it it this way:

You're inside your car waiting for the traffic light to turn green. Now you look ahead across the crossroad junction and you saw a an interesting person who catches your eye. (Say, a beautiful lady). Now it is the turn for the east side of the junction to move, and cars are passing in front of you. When a small car passes in front of you, you'll have to wait until the car passes through before you're able to see that lady in front. A car is much smaller than a bus, so, when a bus took its time to cross the road, perhaps that person has already slipped through your eyes, and there's that "oh-well" sigh.

Similarly, lunar eclipse happen because the earth is blocking the sun's light (in the analogy, the beautiful lady being the light source - sun), and solar eclipse is the moon blocking the sun's light. Since the moon is much smaller than the earth, naturally the length of lunar eclipse is much longer compared to solar eclipse.

Another interesting fact explains the mystery why the moon does not completely disappear but instead, appears to be amber or sometimes coppery-red when totality occurs. This is interesting because during solar eclipse, all that we see is a sun being 'eaten' by the moon and nothing in particular happened on the dark shadowed area of the sun.

In a lunar eclipse, the earth blocked the sun's ray. But the earth does not completely block all the light from the sun. A little part of the sunlight passed through the surface of the earth and the light is refracted due to earth's atmosphere which acts like a prism. (refraction of light is the same process that produced the rainbow where the water in the air acts like a prism which split light from sun into the familiar rainbow colours) The refraction of light produced a rainbow likened light which consist of mostly red and blue. This light is then beamed to the moon where during totality (when moon is completely shadowed by earth), the red part of that refracted light hit the surface of the moon, hence the red appearance.

The explanation of the light rays can be better explained graphically HERE.

1 comment:

Anonymous said...

welcome back.