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BAA Observing calendar

Mercury at superior solar conjunction

Saturday, 2018, February 17 - 12:12

Dominic Ford – originally published on In-The-Sky.org

From our vantage point on the Earth, Mercury will appear very close to the Sun in the sky as it passes around the far side of the solar system from the Earth.

At closest approach, Mercury and the Sun will appear at a separation of only 1°58', making Mercury totally unobservable for several weeks while it is lost in the Sun's glare.

Mercury will also pass apogee – the time when it is most distant from the Earth – within a few days of the same time, since it will lie exactly opposite to the Earth in the Solar System. It will move to a distance of 1.38 AU from the Earth, making it appear small and very distant. If it could be observed, it would measure 4.9 arcsec in diameter, whilst appearing completely illuminated.

Mercury's reaching superior conjunction marks the end of its apparition in the morning sky and its transition to become an evening object over the next few weeks.

The exact position of Mercury at the moment it passes solar conjunction will be:

Object Right Ascension Declination Constellation Angular Size
Mercury 22h05m30s -13°50' Aquarius 4.9"
Sun 22h02m -11°59' Aquarius 32'22"

The coordinates above are given in J2000.0.


The details of this observing event were provided courtesy of In-The-Sky.org

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