Thursday, February 21, 2008

Lunar eclipse

Did you see last night's total lunar eclipse? It was a lot of fun. The total eclipse phase started in our area at around 7:11pm, a very convenient time to watch it with our kids. I got home from work a little before that, bundled everyone into the car, and drove to the north end of Shoreline Park for a clear view of the sky. We've been having rain lately, so there was a good chance that our view would be obscured by clouds. Fortunately, the clouds cooperated, and we saw the eclipsed moon quite clearly in the sky!

I was a little concerned that during the total eclipse we wouldn't see the moon at all (in which case how would I convince my kids that anything was actually happening...:-). But that's not what happens: you could clearly see a faint, reddish light on the moon. Why can you see the moon during a total eclipse? Wikipedia has the answer:

The Moon does not completely disappear as it passes through the umbra because of the refraction of sunlight by the Earth's atmosphere into the shadow cone; if the Earth had no atmosphere, the Moon would be completely dark during an eclipse.

And why does the Moon appear reddish during the eclipse?

The red colouring arises because sunlight reaching the Moon must pass through a long and dense layer of the Earth's atmosphere, where it is scattered. Shorter wavelengths are more likely to be scattered by the small particles, and so by the time the light has passed through the atmosphere, the longer wavelengths dominate. This resulting light we perceive as red.

I took my camera along to take a photograph of the eclipse. Unfortunately, I failed. Even though I figured out the setting to keep the shutter open for as long as I wanted, and even though I had a small tripod to stabilize the camera, I was unable to force the camera to actually take a photograph, i.e., the shutter didn't actually open...:-( Not sure what I was doing wrong. But I have two friends in my office who are master photographers (check out some of Simon's amazing photographs)! I'm sure they'll educate me on what I did wrong.

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