Dominic Ford, Editor
From the Eclipses feed
There will be a partial eclipse of the Moon, though it will not be visible from Ashburn since the Moon will be beneath the horizon at the time.
The eclipse will last from 15:54 until 16:21, and maximum eclipse will occur at 16:08, when 1% of the Moon's disk will lie in shadow (all times given in Ashburn time).
Eclipses of the Moon are easy to watch with the unaided eye. A modest pair of binoculars will give a superb view of the Moon's surface, but are not required. Unlike solar eclipses, lunar eclipses are entirely safe to look at without the need to look through any kind of filter.
They occur whenever the Earth passes between the Moon and Sun, such that it obscures the Sun's light and casts a shadow onto the Moon's surface. The circular shadow cast by the Earth appears as a bite taken out of the Moon during its partial phases.
Sequence of events
The eclipse will begin at 14:04, when the Moon first enters a region of the Earth's shadow called the penumbra. In this outer part of the Earth's shadow, an observer on the Moon would see the Sun partially obscuring the Sun's disk, but not completely covering it. As a result the Moon's brightness will begin to dim, as it is less strongly illuminated by the Sun, but it remains illuminated.
At 15:54, the edge of the Moon's disk will enter the Earth's umbra. This is the region of space in which an observer on the Moon's surface would see the Earth completely obscuring the whole of the Sun's disk, and would find themselves suddenly thrust into darkness.
As an increasing fraction of the Moon's face creeps into the Earth's umbra, it will appear to have a growing bite taken out of it. We will see our planet's circular shadow sweep across the face of the Moon.
The table below lists the times when each part of the eclipse will begin and end.
|14:04||18:04||Moon begins to enter the Earth's penumbra|
|15:54||19:54||Moon begins to enters the Earth's umbra. Partial eclipse begins.|
|16:21||20:21||Moon fully outside the Earth's umbra. Partial eclipse ends.|
|18:11||22:11||Moon leaves the Earth's penumbra|
Visibility of the eclipse
Eclipses of the Moon are visible anywhere where the Moon is above the horizon at the time. Since the geometry of lunar eclipses requires that the Moon is directly opposite the Sun in the sky, the Moon can be seen above the horizon anywhere where the Sun is beneath the horizon. The map below shows where the eclipse of April 25 will be visible.
This eclipse is a member of Saros series 112. The exact position of the Moon at the moment of greatest eclipse is as follows:
|Object||Right Ascension||Declination||Constellation||Angular Size|
The coordinates above are given in J2000.0.
|The sky on 25 April 2013|
15 days old
All times shown in EDT.
Espanak, F., & Meeus, J., Five Millennium Canon of Lunar Eclipses: -1999 to +3000, NASA Technical Publication TP-2009-214172 (2009)
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|25 Apr 2013, 15:58 EDT||– Full Moon|
|02 May 2013, 07:15 EDT||– Moon at Last Quarter|
|09 May 2013, 20:30 EDT||– New Moon|
|18 May 2013, 00:36 EDT||– Moon at First Quarter|
© Collin Grady from Las Vegas, Nevada.