None available.

Penumbral 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 penumbral 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 09:07 until 13:28, and maximum eclipse will occur at 11:18 (all times given in Ashburn time).

A penumbral eclipse

Like other lunar eclipses, penumbral eclipses 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. But unlike other kinds of eclipses, they are extremely subtle events to observe.

In a penumbral eclipse the Moon passes through an outer region of the Earth's shadow called the penumbra. This is the outer part of the Earth's shadow, in which the Earth appears to cover part of the Sun's disk, but not all of it (see diagram below). As a result, the Moon's brightness will begin to dim, as it is less strongly illuminated by the Sun, but the whole of the Sun's disk will remain illuminated to some degree.

Although the Moon's light dims considerably during a penumbral eclipse, this is only perceptible to those with very astute vision, or in carefully controlled photographs.

This is a rare occasion when the whole of the Moon's face will pass within the Earth's penumbra, and so the reduction of the Moon's brightness will be more perceptible than usual. Such events are called total penumbral lunar eclipses, and are rare because the statistical chance that the Moon will enter the Earth's umbra at some point is very high once it has passed fully within its penumbra, and this makes an eclipse a partial lunar eclipse.

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 January 31 will be visible.

Map of where the eclipse of January 1999 will be visible.
Map of where the eclipse of January 1999 will be visible. Click here to expand.

The table below lists the times when each part of the eclipse will begin and end.

Local
time
UTC
09:0714:07Moon begins to enter the Earth's penumbra
11:1816:18Greatest eclipse
13:2818:28Moon leaves the Earth's penumbra

This eclipse is a member of Saros series 114. The exact position of the Moon at the moment of greatest eclipse is as follows:

Object Right Ascension Declination Constellation Angular Size
The Moon 08h54m +16°25' Cancer 31'33"

The coordinates above are given in J2000.0.

The sky on 17 August 2018
Sunrise
06:23
Sunset
20:01
Twilight ends
21:41
Twilight begins
04:44

6-day old moon
Waxing Crescent

42%

6 days old

Planets
Rise Culm. Set
Mercury 05:26 12:17 19:08
Venus 10:16 16:01 21:46
Moon 13:20 18:41 00:02
Mars 19:06 23:34 04:06
Jupiter 13:05 18:17 23:28
Saturn 16:51 21:35 02:23
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_199901.png

Related news

31 Jan 1999, 11:08 EST  –  Full Moon
08 Feb 1999, 06:59 EST  –  Moon at Last Quarter
16 Feb 1999, 01:40 EST  –  New Moon
22 Feb 1999, 21:44 EST  –  Moon at First Quarter

Image credit

None available.

Ashburn

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39.04°N
77.49°W
EDT

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