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Close approach of the Moon and Mercury

Dominic Ford, Editor
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The sky at

The Moon and Mercury will make a close approach, passing within 0°01' of each other. The Moon will be 28 days old.

From Ashburn, the pair will be visible in the dawn sky, rising at 05:36 (EDT) – 1 hour and 21 minutes before the Sun – and reaching an altitude of 11° above the eastern horizon before fading from view as dawn breaks around 06:39.

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The Moon will be at mag -8.4; and Mercury will be at mag -1.0. Both objects will lie in the constellation Leo.

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

At around the same time, the pair will also share the same right ascension – called a conjunction.

A graph of the angular separation between the Moon and Mercury around the time of closest approach is available here.

The positions of the pair at the moment of closest approach will be as follows:

Object Right Ascension Declination Constellation Magnitude Angular Size
The Moon 10h49m30s +09°04' Leo -8.4 31'34"9
Mercury 10h49m30s +09°06' Leo -1.0 6"0

The coordinates above are given in J2000.0. The pair will be at an angular separation of 15° from the Sun, which is in Virgo at this time of year.

The sky on 18 September 2017
Twilight ends
Twilight begins

28-day old moon
Waning Crescent


28 days old

Rise Culm. Set
Mercury 05:34 12:07 18:41
Venus 04:36 11:22 18:08
Moon 05:15 11:52 18:30
Mars 05:26 12:01 18:35
Jupiter 09:20 14:54 20:28
Saturn 13:55 18:41 23:28
All times shown in EDT.


Never attempt to point a pair of binoculars or a telescope at an object close to the Sun. Doing so may result in immediate and permanent blindness.


The circumstances of this event were computed using the DE405 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

15 Sep 2017  –  Mercury at perihelion
08 Oct 2017  –  Mercury at superior solar conjunction
29 Oct 2017  –  Mercury at aphelion
23 Nov 2017  –  Mercury at greatest elongation east

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