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To: justiceseeker93
P stands for penumbra and U for umbra. If you were on the moon, the penumbral phase would mean that the sun was partly hidden by the earth. The umbral phase would mean the sun was completely hidden by the earth.

For earth-bound observers, the penumbral stage is not very striking--the moon's surface should be somewhat darker than normal but you're seeing a part of the moon that is still getting some sunlight. The umbral phase is darker and more noticeable.

From the map, it looks like the moon sets over Chicago shortly after the start of the umbral stage, so it may not be worth getting up early for. Even in the Pacific time zone, the eclipse will be partial--the earth's shadow will be noticeable but won't cover the entire earth-facing surface of the moon.

Two weeks from now (July 11) there will be total eclipse of the sun, but the path of totality goes mostly over the south Pacific--totality will be visible from Easter Island and from some remote parts of southern Chile and southern Argentina (assuming the skies are clear).

18 posted on 06/25/2010 4:28:30 PM PDT by Verginius Rufus
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To: Verginius Rufus

The P1 line represents where the penumbra begins to be visible at moonset. The U1 line represents where the umbra begins to be visible at moonset. Between those two lines people can see only the penumbral phase. The U4 line represents where the umbral phase ends at moonset, and the P4 line where the penumbral phase ends at moonset. West of the P4 line people can see the entire eclipse...but of course it is only a partial eclipse.


19 posted on 06/25/2010 4:35:43 PM PDT by Verginius Rufus
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To: Verginius Rufus

Thanks for the info. I thought that was it but wasn’t sure. Now what do the “1” and “4” in the notion on the map indicate?


20 posted on 06/25/2010 4:36:34 PM PDT by justiceseeker93
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To: Verginius Rufus

Thanks for the info. I thought that was it but wasn’t sure. Now what do the “1” and “4” in the notation on the map indicate?


21 posted on 06/25/2010 4:36:52 PM PDT by justiceseeker93
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