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 A
Lunar Eclipse is a natural phenomenon. It occurs when the Earth falls in
direct alignment with the Sun and the Moon, resulting in the Moon's
passing into the shadow of the Earth.
During a lunar eclipse, the Sun and the Moon should travel to the opposite
side in the sky (about 180° apart from each other). In other word, lunar
eclipse can only occur during full moon ( around about 15th of a lunar
month ). Why doesn't lunar eclipse occur every month?
The answer is quite complicated. The Sun and the Moon travel around the
sky in a circular paths called ecliptic and the moon's path. However, the
moon's path is tilted about 5° to the ecliptic, making the alignment of
the Sun, the Earth and the Moon in a straight line a relatively rare case.
Only when the Sun and the Moon are close enough to the nodes (crossing
points of the ecliptic and the moon's paths) during full moon, a lunar
eclipse can occur.
There are three types of lunar eclipse: total lunar eclipse, partial lunar
eclipse and penumbral lunar eclipse. When the Moon totally enters the
umbra (the full shadow) of the Earth, it is a total lunar eclipse; When
only part of the moon passes into the umbra, it is a partial lunar
eclipse; As to the penumbral lunar eclipse, it describe a phenomenon when
the Moon only enters the penumbra (the partial or incomplete shadow) of
the Earth. During a penumbral lunar eclipse, the brightness of the Moon is
only marginally reduced. As it is nearly unnoticeable to the naked eyes,
it doesn't draw much public attention.
As the size of the umbra of the Earth is much larger than the Moon, the
Moon is always totally inside the Earth's shadow during total lunar
eclipse. Hence there is no such thing as "annular lunar
eclipse".
Total lunar eclipse goes
through seven stages:
Moon enters penumbra : Instant of first external tangency of Moon with the
penumbra.
Moon enters umbra : Instant of
first external tangency of Moon with the umbra.
Total eclipse begins :
Instant of first internal tangency of Moon with the umbra.
The greatest
eclipse : The moment when the centre of the Moon is the closest to the
centre of the Earth's shadow.
Total eclipse ends : Instant of last
internal tangency of the Moon with the umbra.
Moon leaves umbra :
Instant of last external tangency of the Moon with the umbra.
Moon
leaves penumbra : Instant of last external tangency of the Moon with the
penumbra. It marks the end of the lunar eclipse.
For
more detail, you can go to "Nature
of the Universe " Chapter 7 ─ The Moon and Eclipses
in Teacher's
Corner.
Forthcoming lunar eclipse from 2012 to
2020:
| Date 1 |
Type |
Hong
Kong |
Hong
Kong Time 2 |
Mag. 3 |
Moonrise |
Moonset |
| 04/06/2012 |
Partial
|
Eclipse at
Moonrise
|
5:59pm -
8:07pm |
0.376 |
7:00pm
(04/06) |
6:12am
(05/06) |
| 28/11/2012 |
Penumbral
|
Visible
|
8:13pm
-12:53am |
0.942 |
5:28pm
(28/11) |
7:04am
(29/11) |
| 26/04/2013 |
Partial
|
Visible
|
3:52am -
4:23am |
0.02 |
6:20pm
(25/04) |
5:59am
(26/04) |
| 25/05/2013 |
Penumbral
|
Invisible
|
11:43am
- 12:37pm |
0.041 |
7:13pm
(25/05) |
5:31am
(25/05) |
| 19/10/2013 |
Penumbral |
Eclipse at
Moonset
|
5:48am -
9:52 am |
0.791 |
5:25pm
(18/10) |
6:22am
(19/10) |
| 15/04/2014 |
Total
|
Invisible
|
1:58pm
- 5:33pm |
1.295 |
6:47pm
(15/04) |
5:49am
(15/04) |
| 08/10/2014 |
Total
|
Eclipse
at Moonrise
|
5:14pm -
8:35pm |
1.172 |
5:59pm
(08/10) |
6:50am
(09/10) |
| 04/04/2015 |
Total
|
Eclipse
at Moonrise
|
6:15pm
- 9:45pm |
1.006 |
6:33pm
(04/04) |
6:34am
(05/04) |
| 28/09/2015 |
Total
|
Invisible
|
9:07am -
12:27pm |
1.282 |
6:28pm
(28/09) |
6:04am
(28/09) |
| 23/03/2016 |
Penumbral
|
Eclipse
at Moonrise
|
5:37pm
- 9:57pm |
0.801 |
6:29pm
(23/03) |
6:46am
(24/03) |
| 17/09/2016 |
Penumbral
|
Visible
|
12:53am
- 4:56am |
0.933 |
6:09pm
(16/09) |
6:22am
(17/09) |
| 11/02/2017 |
Penumbral
|
Eclipse
at Moonset
|
6:32am
- 10:55am |
1.014 |
5:40pm
(10/02) |
6:54am
(11/02) |
| 08/08/2017 |
Partial
|
Visible
|
1:22am
- 3:19am |
0.251 |
6:41pm
(07/08) |
6:10am
(08/08) |
| 31/01/2018 |
Total
|
Visible
|
7:48pm
- 11:12pm |
1.312 |
5:59pm
(31/01) |
7:26am
(01/02) |
| 28/07/2018 |
Total
|
Eclipse
at Moonset
|
2:24am
- 6:19am |
1.614 |
6:45pm
(27/07) |
6:00am
(28/07) |
| 21/01/2019 |
Total
|
Invisible
|
11:34am
- 2:51pm |
1.201 |
6:14pm
(21/01) |
6:54am
(21/01) |
| 17/07/2019 |
Partial
|
Eclipse
at Moonset
|
4:01am
- 7:00am |
0.658 |
6:47pm
(16/07) |
5:52am
(17/07) |
| 11/01/2020 |
Penumbral
|
Visible
|
1:06am
- 5:14am |
0.921 |
5:28pm
(10/01) |
7:20am
(11/01) |
| 06/06/2020 |
Penumbral
|
Visible
|
1:44am -
5:07am |
0.593 |
6:38pm
(05/06) |
5:50am
(06/06) |
| 05/07/2020 |
Penumbral
|
Invisible
|
11:04am
- 1:55pm |
0.38 |
7:27pm
(05/07) |
5:29am
(05/07) |
| 30/11/2020 |
Penumbral
|
Eclipse at Moonrise
|
3:30pm -
7:56pm |
0.855 |
5:38pm
(30/11) |
7:18am
(01/12) |
1
The date showed in the table is the time for the "Moon enters umbra"
or the "Moon enters penumbra".
2
For Total / Patial lunar eclipse, the time period is for the "Moon
enters umbra" to "Moon leaves embra". For Penumbral lunar
eclipse, the time period is for the "Moon enters penumbra" to
"Moon leaves penumbra".
3
For Penumbral lunar eclipse, Magnitude is equal to Penumbral Magnitude.
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