© Collin Grady from Las Vegas, Nevada.

Partial lunar eclipse

Dominic Ford, Editor
From the Eclipses feed

Time:       Altitude: °      Azimuth: °

A simulation of how the eclipse will appear from Ashburn.

The outer grey circle is the Earth's penumbra, and the inner black circle is the umbra. Any part of the Moon which passes within the black circle will be unilluminated, while any part within the grey circle will appear less bright than usual.




There will be a partial eclipse of the Moon, visible from Ashburn in the southern sky. The Moon will lie 30° above the horizon at the moment of greatest eclipse.

The eclipse will last from 23:25 until 02:08, and maximum eclipse will occur at 00:47, when 55% 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 22:07, 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 23:25, 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.

Local
time
UTC
22:0702:07Moon begins to enter the Earth's penumbra
23:2503:25Moon begins to enters the Earth's umbra. Partial eclipse begins.
00:4704:47Greatest eclipse
02:0806:08Moon fully outside the Earth's umbra. Partial eclipse ends.
03:2607:26Moon leaves the Earth's penumbra
The geometry of a lunar eclipse
The geometry of a lunar eclipse. Within the penumbra, the Earth covers some fraction of the Sun's disk, but not all of it. In the umbra, the Earth covers the entirity of the Sun's disk. Any parts of the Moon's surface that lie within the Earth's umbra will appear unilluminated. Image courtesy of F. Sogumo.

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 July 17 will be visible.

Map of where the eclipse of July 1981 will be visible.
Map of where the eclipse of July 1981 will be visible. Click here to expand.

Further information

This eclipse is a member of Saros series 119. The exact position of the Moon at the moment of greatest eclipse is as follows:

Object Right Ascension Declination Constellation Angular Size
The Moon 19h46m -20°31' Sagittarius 30'26"

The coordinates above are given in J2000.0.

The sky on 21 May 2018
Sunrise
05:51
Sunset
20:19
Twilight ends
22:10
Twilight begins
04:00

6-day old moon
Waxing Crescent

39%

6 days old

Planets
Rise Culm. Set
Mercury 05:09 11:59 18:49
Venus 07:50 15:23 22:55
Moon 12:25 19:15 01:22
Mars 00:45 05:31 10:18
Jupiter 18:57 00:12 05:23
Saturn 22:59 03:49 08:34
All times shown in EDT.

Source

Espanak, F., & Meeus, J., Five Millennium Canon of Lunar Eclipses: -1999 to +3000, NASA Technical Publication TP-2009-214172 (2009)

You may embed the map above in your own website. It is licensed under the Creative Commons Attribution 3.0 Unported license, which allows you to copy and/or modify it, so long as you credit In-The-Sky.org.

You can download it from:
https://in-the-sky.org/news/eclipses/lunar_198107.png

Related news

17 Jul 1981, 00:40 EDT  –  Full Moon
24 Jul 1981, 05:41 EDT  –  Moon at Last Quarter
30 Jul 1981, 23:53 EDT  –  New Moon
07 Aug 1981, 15:27 EDT  –  Moon at First Quarter

Image credit

© Collin Grady from Las Vegas, Nevada.

Ashburn

Latitude:
Longitude:
Timezone:

39.04°N
77.49°W
EDT

Color scheme