Penumbral lunar eclipse

Dominic Ford, Editor
From the Eclipses feed


Objects: The Moon

The Moon will pass through the Earth's shadow between 06:49 and 08:28 EDT, creating a penumbral lunar eclipse. The eclipse will be visible any location where the Moon is above the horizon at the time, including from Antarctica, the Americas, Oceania, Eastern and Southeast Asia, south-eastern Russia and Alaska.

It will not be visible from Columbus since the Moon will be beneath the horizon at the time.

Maximum eclipse will occur at 07:39 (all times given in Columbus 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 be reduced, as it is less strongly illuminated by the Sun, but the whole of the Moon's disk will remain illuminated to some degree.

The effect is only perceptible to those with very astute vision, or in carefully controlled photographs.

Moreover, on this occasion no more than 10% 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 the Earth's shadow. Within the Earth's penumbral shadow, the planet covers some fraction the Sun's disk. Only within the smaller umbra does the Earth cover the entirety of the Sun's disk. Any areas of the Moon's surface that pass through the penumbra appear darker than usual as the Earth is obstructing some of the sunlight that usually illuminates them. Areas within the umbra, meanwhile, receive no illumination from the Sun at all.

Timing

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

Local
time
UTC
06:4910:49Moon begins to enter the Earth's penumbra
07:3911:39Greatest eclipse
08:2812:28Moon 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 July 15 will be visible.

Map of where the eclipse of July 1973 will be visible. Click here to expand.

The eclipse geometry

Lunar eclipses occur when the Sun, Earth and Moon are aligned in a straight line, so that the Earth passes between the Sun and Moon and casts a shadow onto the latter's surface.

Each time the Moon orbits the Earth, it passes almost opposite to the Sun in the sky as it reaches Full Moon. If the Moon orbited the Earth in exactly the same plane that the Earth orbits the Sun, the Earth would pass between the Sun and Moon and create a lunar eclipse at Full Moon every month.

The Moon's orbit is tipped up by 5° relative to the Earth's orbit around the Sun, represented by the grid above. Lunar eclipses only occur at full moon if they occur when the Moon is close to the Earth–Sun plane, at points called the Moon's nodes.

In fact, the Moon's orbit is tipped up at an angle of 5° relative to the Earth's orbit around the Sun. This means that the alignment of the Sun—Earth—Moon line at Full Moon usually isn't exact. As a result, an observer on the Moon would see the Earth pass a few degrees to the side of the Sun.

In the diagram to the right, the grid represents the plane of the Earth's orbit around the Sun. As it circles the Earth, the Moon passes through this Earth–Sun plane twice each month, at the points on the left and right labelled as nodes. A lunar eclipse happens only when one of these node crossings happens to coincide with Full Moon. This happens roughly once every six months, usually two weeks before or after a solar eclipse.

Further information

This eclipse is a member of Saros series 148. The position of the Moon at the moment of greatest eclipse is as follows:

Object Right Ascension Declination Constellation Angular Size
The Moon 19h39m 20°05'S Sagittarius 29'35"

The coordinates above are given in J2000.0.

Next/previous eclipses

« Previous Next »
Visible from the Contiguous United States Worldwide Worldwide Visible from the Contiguous United States
18 Jan 1973 15 Jun 1973 Penumbral Lunar Eclipses 06 Nov 1976 06 Nov 1976
18 Jan 1973 15 Jun 1973 Lunar Eclipses 10 Dec 1973 10 Dec 1973
18 Jan 1973 30 Jun 1973 Eclipses 10 Dec 1973 10 Dec 1973

The sky on 23 Nov 2024

The sky on 23 November 2024
Sunrise
07:24
Sunset
17:09
Twilight ends
18:45
Twilight begins
05:48


Waning Crescent

41%

22 days old

Planets
Rise Culm. Set
Mercury 09:12 13:43 18:13
Venus 10:48 15:19 19:50
Moon 00:03 06:55 13:36
Mars 21:31 04:51 12:10
Jupiter 18:04 01:28 08:51
Saturn 13:43 19:16 00:49
All times shown in EST.

Source

[1] – 

The lunar eclipse predictions presented on this website were computed using EphemerisCompute.

This is an open-source tool which traces the positions of the Sun, Earth and Moon over the course of each eclipse and traces the path of the Moon through the Earth's shadow. It was written by the author and freely available for download from GitHub.

It takes the positions of each body from the JPL DE430 planetary ephemeris.

[2] – 

Espanak, F., & Meeus, J., Five Millennium Canon of Solar Eclipses: -1999 to +3000, NASA Technical Publication TP-2006-214141 (2006)

[3] – 

The list of countries from which the eclipse is visible was computed on the basis of shape files available from DIVA-GIS.

License

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_19730715.png

Related news

07 Jul 1973  –  Moon at First Quarter
15 Jul 1973  –  Full Moon
22 Jul 1973  –  Moon at Last Quarter
29 Jul 1973  –  New Moon

Image credit

None available.

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