The Dark Side of the Moon

If you enjoy looking up at the night sky get ready for a show tonight. A total eclipse of the moon will occur between 9:01 pm CST and 9:51 pm CST.

At 6:35 pm CST the east facing edge of the moon will enter the outer edge of the earth's shadow. At this point it is unlikely that you will be able to see any change. The outer portion (penumbra) of the earth's shadow is far brighter than the center portion (umbra).

At 7:43 pm CST the east-facing edge will enter the dark center portion (umbra) of the earth's shadow. Over the next 78 minutes you can watch the dark shadow of the earth slowly overtake the surface of the moon. At 9:01 pm CST the moon's entire surface will be covered by the earth's dark umbra.

Due to the distance between the sun, earth, and moon the earth is large enough that if it didn't have an atmosphere the moon would practically disappear into the night sky. However (fortunate for us) the earth does have an atmosphere. The sunlight that hits the daytime side of the earth lights up this atmosphere and the mostly transparent air acts like a lens to bend the sunlight around the earth and allow some of it to escape on the unlit side of the earth. Because this light must pass through so much of the atmosphere, much like a sunrise or sunset, the redder portion of the sunlight is what survives the trip around the earth the best. If you were standing in the earth's shadow on the moon, looking up at the earth in the sky, you would see a ring of red light surrounding the earth. This red light shines on the darkened moon's surface giving the moon a red glow. Depending on the condition of the earth's atmosphere (storms, pollution, dust, etc) at the time of the eclipse this will range anywhere from a barely perceptible pink hue to an almost blood like red to a deep dark maroon.

Fifty minutes later at 9:51 pm CST the east-facing edge will exit the dark umbra of the earth's shadow and begin to brighten up in the penumbra. The moons surface will slowly brighten from it's east facing edge to it's west facing edge over the next 78 minutes. By 11:09 pm CST the moon will be entirely in the penumbra and the eclipse will likely be imperceptible again. The moon will finally leave the earth's shadow entirely at 12:17 pm CST.

The entire process will take over 5 and a half hours from 6:35 pm to 12:17 pm CST. The part of the show that is most noticeable will happen slowly over a bit less than 3 and a half hours from 7:43 pm to 11:09 pm CST. If you are not completely enthralled by the activities in the sky, this might get a bit boring. I'd suggest taking a look at the full moon at least once sometime between sunset and 7:43 pm CST just to remind your mind exactly what a brilliant full moon looks like. Then head back out at least once between 8:00 pm and 8:45 pm CST (set an alarm so you don't forget). Each time you look during this period of time you'll notice more of the moon disappearing. Finally, head back out as close to 9:26 pm CST as you can (set another alarm). At that time the moon will be as deep in the shadow as it is going to get. The is when you'll best notice any reddening of the moon. Everything after that is just the reverse of what you've already seen. Of course this means that if you forget to take a look between 8:00 pm and 8:45 pm CST, you'll get a second chance between 10:00 pm and 10:45 pm.

I hope to get my telescopes set up in the driveway to take a look tonight, and I'll probably put the digital camera's out on tri-pods as well. I'm not sure how well the cameras will work in the bitter temperatures predicted this evening in my area, but if I get any good pictures I'll post them.