There will be a total eclipse of the Moon, visible from Ashburn in the western sky. The Moon will lie 47° above the horizon at the midpoint of the eclipse.
The Moon will be totally eclipsed from 02:42 until 03:54, and there will be a partial eclipse visible from 01:34 until 05:02 (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.
When the Moon's disk lies entirely in shadow, it often takes on a spectacular reddy-brown color, as some of the Sun's red light is bent around the edge of the Earth's globe by its atmosphere.
Sequence of events
The eclipse will begin at 00:30, 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 01:34, 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.
Eventually the Moon will pass entirely within the Earth's umbra at 02:42, and the total eclipse will begin.
The table below lists the times when each part of the eclipse will begin and end.
|00:30||05:30||Moon begins to enter the Earth's penumbra|
|01:34||06:34||Moon begins to enters the Earth's umbra. Partial eclipse begins.|
|02:42||07:42||Moon fully within Earth's umbra. Total eclipse begins.|
|03:18||08:18||Midpoint of eclipse|
|03:54||08:54||Moon begins to leave the Earth's umbra. Total eclipse ends.|
|05:02||10:02||Moon fully outside the Earth's umbra. Partial eclipse ends.|
|06:05||11:05||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 December 21 will be visible.
This eclipse is a member of Saros series 125. The exact position of the Moon at the midpoint of the eclipse is as follows:
|Object||Right Ascension||Declination||Constellation||Angular Size|
The coordinates above are given in J2000.0.
|The sky on 21 January 2018|
All times shown in EST.
Espanak, F., & Meeus, J., Five Millennium Canon of Lunar Eclipses: -1999 to +3000, NASA Technical Publication TP-2009-214172 (2009)
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|21 Dec 2010, 03:15 EST||– Full Moon|
|27 Dec 2010, 23:20 EST||– Moon at Last Quarter|
|04 Jan 2011, 04:04 EST||– New Moon|
|12 Jan 2011, 06:33 EST||– Moon at First Quarter|
© John Buonomo, North Billerica, MA.