Mercury and Mars will share the same right ascension, with Mercury passing 4'48" to the south of Mars.
From Cambridge however, the pair will not be observable – they will reach their highest point in the sky during daytime and will be 2° below the horizon at dusk.
Mercury will be at mag -0.5, and Mars at mag 1.8, 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 Mercury and Mars 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 |
| Mercury | 10h57m00s | 7°41'N | Leo | -0.5 | 5"2 |
| Mars | 10h57m00s | 7°46'N | Leo | 1.8 | 3"5 |
The coordinates above are given in J2000.0. The pair will be at an angular separation of 16° from the Sun, which is in Leo at this time of year.
The sky on 19 Aug 2021
| The sky on 19 August 2021 | ||||||||||||||||||||||||||||||||||
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90% 11 days old |
All times shown in EDT.
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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.
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Image credit
The Moon in conjunction with Venus and Jupiter, with the Very Large Telescope in the foreground. Image © Y. Beletsky, ESO, 2009.