Dec 20, 2010 09:01 GMT  ·  By
Russell Croman, Austin, Texas captured the Oct. 27, 2004 total lunar eclipse by stages. The Moon turned red during totality.
   Russell Croman, Austin, Texas captured the Oct. 27, 2004 total lunar eclipse by stages. The Moon turned red during totality.

Today's the big day, or should I say tonight's the night when sky watchers should be able to see the total lunar eclipse you might have already heard of.

If you're interested in watching this very rare event you will have the chance of admiring it tonight, but you should also know what to look for.

This being said, here is a list of the 12 steps of a total lunar eclipse, and even though all of them may not occur tonight – since eclipses are different from one another, you will be able to spot those that will:

1. The moon enters the penumbra – at 12:29 am EST/9:29 pm PST

The shadow of the Earth has two parts: the umbra – the darker inner part, and the penumbra – the lighter outer portion surrounding its shadow.

Only forty-five minutes after the beginning of the eclipse, sky watchers will be able to see something happening to the moon, since the penumbral shadow of the Earth is so faint that it stays invisible until it reaches over 70% of the moon's disk.

2. The penumbral shadow starts appearing (1:13 am EST/10:13 pm PST)

Since the moon is far enough into the penumbra, you should be able to see it on its disk, so begin searching for a faint light shading on its upper left side, that will only become more obvious as time passes.

The shading will look like it's spreading and deepening, and just before entering the Earth's dark umbral shadow the penumbra should appear like a spot on the moon's left portion.

3. Moon enters umbra (1:33 am EST/10:33 pm PST)

Now, the moon starts to cross into the Earth's umbra, and a small dark shape appears on its upper left-hand (northeastern) limb, according to SPACE.com.

This is the beginning of the partial phase of the eclipse, and the umbra becomes much darker than the penumbra and rather sharp-edged.

The shadow will start covering the moon, and even if at first the moon's limb seems to disappear inside of the umbra, as it moves in deeper later on, you should see it becoming orange, red or brown.

4. 75% coverage (2:23 am EST/11:23 pm PST)

With only a quarter of the moon to go, the part covered by the shadow should start to slowly light up, usually in shades of red and gray, but also brown, blue and other tints sometimes.

5. The 'Japanese lantern effect' (2:37 am EST/11:37 pm PST)

Just before and after totality, the difference between the remaining pale-yellow part of the moon and its ruddy-brown coloration can cause the 'Japanese lantern effect'.

6. Total eclipse begins (2:41 am EST/11:41 pm PST)

As the moon fully enters the umbra, the total eclipse begins, but it is not clear how it will look this time.

During a total lunar eclipse, the moon is visible because the sunlight is refracted around the edge of the Earth by the atmosphere, so the clearer the atmosphere, the brighter the moon.

It's just that this year, with the two eruptions (the Eyjafjallajökull volcano in Iceland last spring and the Merapi volcano in Indonesia in October), there might be one or two clouds of ash and dust, floating high above the Earth.

This is why, this year, the moon can look darker than usual, and even have some parts so dark that they become invisible.

7. Middle of totality (3:17 am EST/12:17 am PST)

At this point, the moon is shining 10,000 to 100,000 times fainter than just a couple of hours before, its lower half should be dark with hues or chocolate brown or deep cooper, and its upper portion should be brighter, with hues of oranges, reds and even light blues.

Before the moon was covered by the Earth's shadow, its sunlit surface temperature at the equator was somewhere around 127ºC (260ºF), but since there is no atmosphere that can maintain the heat, in the middle of totality, the temperature on the moon has dropped to minus 173ºC (280º F).

That's a very impressive 300ºC (500ºF) drop in just two hours.

8. The end of the total eclipse (3:53 am EST/12:53 am PST)

The moon starts coming up behind the shadow, and the 'Japanese lantern effect' appears again.

9. 75% coverage (4:10 am EST/1:10 am PST)

The colors of the moon's disk start to disappear and the retreating shadow becomes black again.

10. Moon leaves umbra (5:01 am EST/2:01 am PST) 11. Penumbra shadow fades away (5:20 am EST/2:20 pm PST) 12. Moon leaves penumbra (6:04 am EST/3:04 pm PST) and this is the official end of the eclipse.

You can see here a table showing the times of all the twelve stages of the eclipse, in different time areas.