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The best Mercury morning apparition of the year for northern-based observers takes place during the last week of September and the first part of October 2016. On September 22nd, those at such latitudes may be able to spot the elusive planet low down above the eastern horizon just before sunrise. Shining at mag. +1.1, Mercury is challenging against the bright dawn twilight but binoculars will help. However, make sure that the Sun is below the horizon before looking.

Mercury as seen by the Messenger space probe (credit - NASA)

The planet's visibility then improves each subsequent morning until greatest elongation west (GEW) is reached on September 28th. On this day, it's positioned 17.9 degrees from the Sun and from mid-northern temperate latitudes will appear 8 degrees above the eastern horizon, 45 minutes before sunrise. Mercury is also noticeably brighter than earlier (mag. -0.4) and continues to brighten.

After GEW, Mercury appears lower each subsequent morning until it's finally lost from view during mid-October. On September 29th, the very thin crescent Moon passes less than a degree south of Mercury. On October 11th, Mercury (mag. -1.1) passes a degree north of Jupiter (mag. -1.7) and the slightly brighter Jupiter may act as a guide to locating Mercury, although both planets will appear low down in the bright twilight sky.

The chart below shows Mercury's morning apparition from latitude 51.5N (e.g. London, England). A similar view exists at other northern temperate latitudes. Mercury is also visible from tropical regions but those in the Southern Hemisphere are out of luck, it's badly placed and not easily observable this time.

Mercury as seen 45 minutes before sunrise during September and October 2016 from latitude 51.5N (credit:- freestarcharts)

See also

The Planets this Month - September 2016