Mercury as Summer Evening Star

Panorama of the western sky with Mercury and the Moon as seen from Chicago 30 minutes after sunset from 2017 JUN 26 to AUG 12 - See article below.

Mercury - Elongations & Altitudes - 2017

The planet’s elongations from the Sun and altitudes above the horizon as viewed from latitude N 42°

Mercury 02 Mercury 03 Mercury 04


Elusive Mercury is presenting its evening apparition in the western sky following its superior conjunction behind the Sun on 2017 JUN 20. This may be a rather mediocre apparition for observers north of the tropics, but a fine one for those further south.

   By the standard of 30 minutes after sunset for Chicago, Mercury achieved its highest altitude of 7.4° on 2017 JUL 18. Through a telescope on JUL 27 it will appear in dichotomy, i.e. 50% illuminated like a Half Moon. Prior to that it will appear gibbous and afterward as a crescent. Mercury will reach its Greatest Eastern Elongation of 27.2° on JUL 29. Apparent retrograde motion in right ascension will commence on AUG 11. While decreasing in brilliance, Mercury will fall to inferior conjunction between Earth and Sun on AUG 26.

   Mercury will appear near Regulus on 2017 JUL 25.

  The Moon will appear near Mercury on 2017 JUL 24 (occultation) & AUG 21.

NOTE: Event dates in this article are for North American Central Time at those moments nearest to 30 minutes after sunset for Chicago.

Mercury Angular Diameter - 2017

Graph of the apparent angular diameter of Mercury measured in arcseconds  -  Distance in AU = 6.68 / angular diameter

Mercury Illumination Phase - 2017

Graph of the percentage of Mercury’s apparent disk illuminated

Mercury Stellar Magnitude - 2017

Graph of the brightness of Mercury measured in stellar magnitude

Mercury 05


© Curt Renz

Mercury 01
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