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Penumbral lunar eclipse

Fri, 07 Aug 1998 at22:25 EDT(7138 days ago)
02:25 UTC

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, visible from Ashburn in the south-eastern sky. The Moon will lie 23° above the horizon at the moment of greatest eclipse.

The eclipse will last from 21:37 until 23:13, and maximum eclipse will occur at 22:25 (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.

Moreover, on this occasion no more than 12% of the Moon's face will pass within the Earth's penumbra, even at the moment of greatest eclipse, making it especially difficult to notice any reduction in the Moon's brightness.

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 August 7 will be visible.

Map of where the eclipse of August 1998 will be visible.
Map of where the eclipse of August 1998 will be visible. Click here to expand.

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

21:3701:37Moon begins to enter the Earth's penumbra
22:2502:25Greatest eclipse
23:1303:13Moon leaves the Earth's penumbra

This eclipse is a member of Saros series 109. The exact position of the Moon at the moment of greatest eclipse is as follows:

Object Right Ascension Declination Constellation Angular Size
The Moon 21h09m -14°49' Capricornus 32'01"

The coordinates above are given in J2000.0.

The sky on 21 February 2018
Sunrise 06:52
Sunset 17:52
Twilight ends
Twilight begins

6-day old moon
Age of Moon
6 days

All times shown in EST.
Rise Culm. Set
Mercury 07:11 12:38 18:05
Venus 07:26 13:03 18:41
Moon 10:18 16:58 23:37
Mars 02:16 07:01 11:47
Jupiter 00:22 05:26 10:31
Saturn 03:47 08:32 13:17


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

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Related news

07 Aug 1998, 22:11 EDT  –  Full Moon
14 Aug 1998, 15:50 EDT  –  Moon at Last Quarter
21 Aug 1998, 22:04 EDT  –  New Moon
30 Aug 1998, 01:08 EDT  –  Moon at First Quarter

Image credit

None available.




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