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

Lunar occultation of Neptune

Dominic Ford, Editor
From the Lunar Occultations feed

Objects: Neptune
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The Moon will pass in front of Neptune, creating a lunar occultation visible from parts of Portugal.

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.

On this occasion, the occultation will be visible from Seattle. It will begin with the disappearance of Neptune behind the Moon at 12:41 PST, though In daylight and at a low altitude of only 1.8 degrees, in the eastern sky. Its reappearance will be visible at 13:19 PST, though In daylight and at a low altitude of 8.1 degrees.

Extreme caution is necessary when pointing binoculars or telescopes at the sky when the Sun is above the horizon, as even a momentary glance at the Sun through such an instrument can cause permanent blindness.

At the time of the occultation, the Moon will be 7 days past new moon and will be 45% illuminated. Neptune will disappear behind the unilluminated side of the Moon and reappear from behind the illuminated side of the Moon.

The map below shows the visibility of the occultation across the world. Separate contours show where the disappearance of Neptune 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.

Outside of the contours, the Moon does not pass in front of Neptune at any time, or is below the horizon at the time of the occultation.

The map below 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.

Map showing where the occultation is visible

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

Object Right Ascension Declination Constellation Magnitude Angular Size
Neptune 22h44m00s -08°57' Aquarius 7.9 0'02"

The coordinates above are given in J2000.0.

The sky on 06 December 2016
Sunrise
07:43
Sunset
16:18
Twilight ends
18:10
Twilight begins
05:51

7-day old moon
Waxing Crescent

44%

7 days old

Planets
Rise Culm. Set
Mercury 09:31 13:28 17:26
Venus 10:57 15:12 19:27
Moon 12:29 17:57 23:25
Mars 11:47 16:38 21:29
Jupiter 02:35 08:13 13:51
Saturn 07:54 12:15 16:36
All times shown in PST.

Source

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

02 Sep 2016  –  Neptune at opposition
01 Mar 2017  –  Neptune at solar conjunction
04 Sep 2017  –  Neptune at opposition
04 Mar 2018  –  Neptune at solar conjunction

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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