The Moon in conjunction with Venus and Jupiter, with the Very Large Telescope in the foreground. Image © Y. Beletsky, ESO, 2009.

Lunar occultation of Mercury

Dominic Ford, Editor
From the Lunar Occultations feed

Objects: Mercury

The Moon will pass in front of Mercury, creating a lunar occultation visible from countries and territories including eastern China, Philippines, northern Indonesia and eastern Malaysia amongst others. Although the occultation will only be visible across part of the world – because the Moon is so close to the Earth that its position in the sky varies by as much as two degrees across the world – a close conjunction between the pair will be more widely visible.

Unfortunately the occultation will not be visible from Ashburn.

The map below shows the visibility of the occultation across the world. Separate contours show where the disappearance of Mercury is visible (shown in red), and where its reappearance is visible (shown in blue). Solid contours show where each event is likely to be visible through binoculars at a reasonable altitude in the sky. Dotted contours indicate where each event occurs above the horizon, but may not be visible due to the sky being too bright or the Moon being very close to the horizon.

Map showing where the occultation is visible

Outside the contours, the Moon will not pass in front of Mercury at any time, or is below the horizon at the time of the occultation. However, a close conjunction between the pair will be visible across much of the world.

The map can be downloaded in PNG , PDF or SVG format. A KMZ file , is also available, which can be opened in Google Earth to provide a higher resolution map.

The animation below shows the path of the occultation across the Earth's globe. The red circle shows where the Moon appears in front of Mercury.

You can download this video in MP4 or OGG format.

A complete list of the countries and territories where the occultation will be visible is as follows:

Country Time span
China 21:15–12:06
Philippines 14:03–17:37
Indonesia 14:50–11:39
Malaysia 22:55–17:14
Japan 18:34–12:11
Taiwan 19:46–11:05
French Polynesia 06:28–13:45
Kiribati 07:32–13:28
Brunei 14:01–16:58
Federated States of Micronesia 18:40–12:14
Samoa 10:22–13:35
Marshall Islands 09:42–12:52
Hong Kong 22:31–04:15
Guam 18:35–06:25
American Samoa 10:24–13:37
Cook Islands 08:00–13:44
South Korea 19:14–11:42
Northern Mariana Islands 18:34–06:24
Niue 10:26–13:35
Palau 18:52–18:02
Tonga 10:25–13:29
Tuvalu 10:09–13:22
Wallis and Futuna 10:19–13:29
Kingman Reef 07:29–08:41
Palmyra Atoll 07:29–08:41
Paracel Islands 22:34–04:32
Macao 22:30–04:15
Nauru 09:40–12:52
Baker Island 10:17–13:20
Howland Island 10:17–13:19
Jarvis Island 07:37–08:39
Spratly Islands 13:58–04:49
Tokelau 10:21–13:33
Wake Island 10:08–06:52

Lunar occultations are only ever visible from a small fraction of the Earth's surface. Since the Moon is much closer to the Earth than other celestial objects, its exact position in the sky differs depending on your exact location on Earth due to its large parallax. The position of the Moon as seen from two points on opposite sides of the Earth varies by up to two degrees, or four times the diameter of the full moon.

This means that if the Moon is aligned to pass in front of a particular object for an observer on one side of the Earth, it will appear up to two degrees away from that object on the other side of the Earth.

The position of Mercury at the moment of the occultation will be as follows:

Object Right Ascension Declination Constellation Magnitude Angular Size
Mercury 10h49m30s 9°06'N Leo -1.0 0'06"

The coordinates above are given in J2000.0.

Next/previous occultations

« Previous Next »
Visible from the Contiguous United States Worldwide Worldwide Visible from the Contiguous United States
19 Jul 2001 25 Jul 2017 Occultations of Mercury 03 Nov 2021 03 Nov 2021
12 Sep 2017 12 Sep 2017 Occultations 03 Oct 2017 15 Oct 2017

The sky on 18 Sep 2017

The sky on 18 September 2017
Twilight ends
Twilight begins

28-day old moon
Waning Crescent


28 days old

Rise Culm. Set
Mercury 05:33 12:06 18:39
Venus 04:35 11:21 18:07
Moon 04:58 11:51 18:36
Mars 05:25 11:59 18:34
Jupiter 09:18 14:53 20:27
Saturn 13:54 18:40 23:27
All times shown in EDT.


The circumstances of this event were computed using the DE430 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).

This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.

Related news

13 Sep 2017  –  Mercury at highest altitude in morning sky
23 Nov 2017  –  Mercury at greatest elongation east
28 Nov 2017  –  Mercury at highest altitude in evening sky
29 Dec 2017  –  Mercury at highest altitude in morning sky

Image credit

The Moon in conjunction with Venus and Jupiter, with the Very Large Telescope in the foreground. Image © Y. Beletsky, ESO, 2009.





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