<p>'P' is the penumbra, the zone where the Earth blocks some, but not all, of the Sun's light from reaching the Moon. 'U' is the umbra, the zone where the Earth blocks all of the light from the Sun (see <a href="http://www.mreclipse.com/Special/LEprimer.html" rel="noreferrer">this primer</a>). As the Moon moves across the two zones then you will get various times as the Moon touches those zones. So P1 is where the Moon just starts to touch the penumbral shadow, U1 is where the Moon just touches the umbral shadow cone, U2 is where all the Moon is inside the umbral shadow and the total eclipse begins. Similarly U4 and P4 are where the Moon last touches the umbral and penumbral shadows. Note that the times in the chart are in Universal Time so you need to account for your timezones' difference from UTC.</p>

CC BY-SA 4.0
2018-07-28T19:58:40.490Z
2018-07-28T19:58:40.490Z
astrosnapper
<p>astrosnapper already explained the chart and the Us and Ps, so I'm going to focus on the map.</p>

<p>The map shows you which phase of the eclipse is visible from where. For example Mauritius gets to see the whole eclipse while North America is out of luck and doesn't get to see any.</p>

<p>From my vantage point in Germany I should have been able to see from somewhere between U1 (first contact with core shadow) and U2 (start of totality) till the end.
I cannot see P1, P2 and U1 because the moon is still below the horizon from my point of view.
In the end, some low hanging clouds got in the way of my seeing U2 but I got a very good view of U3 (end of totality).</p>

CC BY-SA 4.0
2018-07-29T20:12:45.453Z
2018-07-29T20:12:45.453Z
Sumyrda - remember Monica
<p>NASA has a page dedicated to lunar eclipses and provides <a href="https://eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2018Jul27T.pdf" rel="nofollow noreferrer">charts</a>. How are these charts to be read? What do P1, P4, U1,... mean? What about the world map below?</p>

<p><a href="https://i.sstatic.net/SOBLp.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/SOBLpm.jpg" alt="enter image description here"></a></p>

<p>Click for full size view</p>

CC BY-SA 4.0
2018-07-31T02:39:20.063Z
Since links tend to break over time and we like to believe that people will be reading our questions and answers for a long time to come, I've included an image of your example. Great question btw!
uhoh
<lunar-eclipse>
How to read an eclipse chart?
usernumber
# How to read an eclipse chart?

(Asked by: username_0 on 2018-07-28)

NASA has a page dedicated to lunar eclipses and provides [charts](https://eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2018Jul27T.pdf). How are these charts to be read? What do P1, P4, U1,... mean? What about the world map below?

[![enter image description here](https://i.sstatic.net/SOBLpm.jpg)](https://i.sstatic.net/SOBLp.jpg)

Click for full size view

**Tags:** lunar-eclipse

> **Comments:**
> **username_1**: Since links tend to break over time and we like to believe that people will be reading our questions and answers for a long time to come, I've included an image of your example. Great question btw!  

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## 2 answers

### Answer by username_3 on 2018-07-29. Score: 4 | Accepted answer

username_2 already explained the chart and the Us and Ps, so I'm going to focus on the map.

The map shows you which phase of the eclipse is visible from where. For example Mauritius gets to see the whole eclipse while North America is out of luck and doesn't get to see any.

From my vantage point in Germany I should have been able to see from somewhere between U1 (first contact with core shadow) and U2 (start of totality) till the end.
I cannot see P1, P2 and U1 because the moon is still below the horizon from my point of view.
In the end, some low hanging clouds got in the way of my seeing U2 but I got a very good view of U3 (end of totality).


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### Answer by username_2 on 2018-07-28. Score: 5

'P' is the penumbra, the zone where the Earth blocks some, but not all, of the Sun's light from reaching the Moon. 'U' is the umbra, the zone where the Earth blocks all of the light from the Sun (see [this primer](http://www.mreclipse.com/Special/LEprimer.html)). As the Moon moves across the two zones then you will get various times as the Moon touches those zones. So P1 is where the Moon just starts to touch the penumbral shadow, U1 is where the Moon just touches the umbral shadow cone, U2 is where all the Moon is inside the umbral shadow and the total eclipse begins. Similarly U4 and P4 are where the Moon last touches the umbral and penumbral shadows. Note that the times in the chart are in Universal Time so you need to account for your timezones' difference from UTC.


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