Conjunction between the Moon and Neptune

2017 May 20

Dominic Ford – originally published on

The Moon and Neptune will make a close approach, passing within 0°27' of each other.

From London (click to change), the pair will be difficult to observe as they will appear no higher than 15° above the horizon. They will be visible in the dawn sky. They will rise at 02:42 (BST), 2 hours and 19 minutes before the Sun, and attain an altitude of 15° above the south-eastern horizon before fading from view as dawn breaks at around 04:34.

At the moment of closest approach, the Moon will be at mag -11.6, and Neptune at mag 7.9, both in the constellation Aquarius.

At closest approach, the pair will be close enough to fit comfortably within the field of view of a telescope, but will also be visible to the naked eye or a through pair of binoculars.

The precise positions of the Moon and Neptune at the moment of closest approach will be as follows:

Object Right Ascension Declination Constellation Magnitude Angular Size
The Moon 23h02m10s -07°36' Aquarius -11.6 31'16"2
Neptune 23h01m40s -07°10' Aquarius 7.9 2"2

The coordinates above are given in J2000.0. The pair will be at an angular separation of 75° from the Sun, which is in Taurus at this time of year.

The details of this observing event were provided courtesy of