© Collin Grady from Las Vegas, Nevada.

Partial lunar eclipse

Dominic Ford, Editor
From the Eclipses feed

Objects: The Moon

Simulation of the eclipse as seen from Cambridge
Time:       Altitude: °      Azimuth: °




The Moon will pass through the Earth's shadow between 22:14 and 23:16 EDT, creating a partial lunar eclipse. The eclipse will be visible any location where the Moon is above the horizon at the time, including from the Americas, Antarctica, Africa, Europe, Western Asia and south-western Russia.

It will be visible from Cambridge in the south-eastern sky. The Moon will lie 38° above the horizon at the moment of greatest eclipse.

Maximum eclipse will occur at 22:45, when 8% of the Moon's disk will lie in shadow (all times given in Cambridge time).

The simulation to the right shows Moon's path relative to the Earth's shadow. The outer grey circle is the Earth's penumbra, within which the Earth blocks part of the Sun's light, making the Moon appear less bright than usual, but not completely dark. The inner black circle is the umbra, within which the Earth entirely blocks the Sun's light, making the Moon's disk appear entirely unilluminated.

By default the eclipse is drawn with the local vertical in Cambridge uppermost (Zenith up), so that it is orientated as you would see it looking up at the Moon. The compass shows the direction of celestial north relative to the local vertical. Alternatively, you can orientate the sky with celestial north orientated uppermost, by selecting the option North up.

Begin typing the name of a town near to you, and then select the town from the list of options which appear below.

Selecting the option Diagram of Moon's path produces a static display of the Moon's path over the duration of the eclipse.

The lower panel shows the Moon's position in the sky relative to the horizon, as seen from Cambridge.

Timing

The eclipse will begin at 20:42, 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 Earth 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 22:14, 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 thrust into night-like darkness.

As an increasing fraction of the Moon's face creeps into the Earth's umbra, we 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
20:4200:42Moon begins to enter the Earth's penumbra
22:1402:14Moon begins to enters the Earth's umbra. Partial eclipse begins.
22:4502:45Greatest eclipse
23:1603:16Moon fully outside the Earth's umbra. Partial eclipse ends.
00:4804:48Moon leaves the Earth's penumbra
The geometry of a lunar eclipse
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.

Observing the eclipse

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.

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 September 17 will be visible.

Map of where the eclipse of September 2024 will be visible.
Map of where the eclipse of September 2024 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 118. The position of the Moon at the moment of greatest eclipse is as follows:

Object Right Ascension Declination Constellation Angular Size
The Moon 23h44m 2°46'S Pisces 33'24"

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
19 Nov 2021 28 Oct 2023 Partial Lunar Eclipses 28 Aug 2026 28 Aug 2026
25 Mar 2024 25 Mar 2024 Lunar Eclipses 14 Mar 2025 14 Mar 2025
08 Apr 2024 08 Apr 2024 Eclipses 02 Oct 2024 14 Mar 2025

The sky on 17 Sep 2024

The sky on 17 September 2024
Sunrise
06:24
Sunset
18:49
Twilight ends
20:25
Twilight begins
04:48

14-day old moon
Waning Gibbous

99%

14 days old

Planets
Rise Culm. Set
Mercury 05:25 11:58 18:31
Venus 08:50 14:21 19:52
Moon 18:50 00:41 06:49
Mars 23:51 07:28 15:05
Jupiter 22:42 06:14 13:46
Saturn 18:32 00:06 05:39
All times shown in EDT.

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_20240918.png

Related news

17 Sep 2024  –  Full Moon
24 Sep 2024  –  Moon at Last Quarter
02 Oct 2024  –  New Moon
10 Oct 2024  –  Moon at First Quarter

Image credit

© Collin Grady from Las Vegas, Nevada.

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