The Moon and Mercury will share the same right ascension, with the Moon passing 1'46" to the south of Mercury. The Moon will be 28 days old.
At around the same time, the two objects will also make a close approach, technically called an appulse.
From Cambridge , the pair will be visible in the dawn sky, rising at 05:06 (EDT) – 1 hour and 19 minutes before the Sun – and reaching an altitude of 10° above the eastern horizon before fading from view as dawn breaks at around 06:08.
The Moon will be at mag -8.4, and Mercury at mag -1.0, both in the constellation Leo.
The pair 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.
A graph of the angular separation between the Moon and Mercury around the time of closest approach is available here.
The positions of the two objects at the moment of conjunction will be as follows:
| Object | Right Ascension | Declination | Constellation | Magnitude | Angular Size |
| The Moon | 10h49m30s | 9°04'N | Leo | -8.4 | 31'34"9 |
| Mercury | 10h49m30s | 9°06'N | 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 Sep 2017
| The sky on 18 September 2017 | ||||||||||||||||||||||||||||||||||
|
0% 28 days old |
All times shown in EDT.
|
|||||||||||||||||||||||||||||||||
Warning
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.
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
| 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.