Mercury, the innermost planet, is now heading towards greatest eastern elongation (GEE), which it reaches on April 1, 2017. From mid-March, observers at northern-based locations should be able to spot the elusive planet, low down above the western horizon just after sunset. Each subsequent evening it improves in visibility until GEE is reached. After that, Mercury sinks gradually back towards the horizon until about 10 days later when it becomes lost to the bright twilight sky. This also happens to be the best evening apparition of the year from northern locations.

From southern latitudes, Mercury is unsuitably placed for observation this time.

Mercury as seen by the MESSENGER space probe (credit:- freestarcharts)

To spot Mercury, a clear unobstructed view of the western horizon is essential. At the time of GEE the planet will shine at mag. -0.2 and be positioned 19 degrees from the Sun. From mid-latitude northern locations, it appears 10 degrees above the western horizon, 45 minutes after sunset. Observers should note that the planet's brightness decreases during the visibility period. For example on March 17th, it will shine at mag. -1.4, but be down to mag. +0.8 by April 6th.

The diagram below shows the altitude of Mercury 45 minutes as seen from latitude of 51.5N (e.g. London, England). A similar view exists at other northern temperate latitudes.

Mercury 45 minutes after sunset from mid-latitude northern locations (credit:- freestarcharts)

Sky Highlights - March 2017

Comet
Comet 41P/Tuttle-Giacobini-Kresak now visible with binoculars as it heads towards perihelion

Mercury
Mercury heading towards greatest elongation east

Minor Planet
Vesta now visible with binoculars and small telescopes.

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for March 2017

Northern Hemisphere
Evening
West:- Venus (mag. -4.8 to -4.1 - first half of month), Mars (mag. +1.3 to +1.5), Uranus (mag. +5.9), Mercury (mag. -1.5 to -0.4 - second half of month)
Midnight
Southeast:- Jupiter (mag. -2.3 to -2.5)
Morning
Southwest:- Jupiter
Southeast:- Saturn (mag. +0.5)

Southern Hemisphere
Evening
West:- Venus (first half of month), Mars, Uranus
Midnight
North:- Jupiter
East:- Saturn
Morning
West:- Jupiter
Northeast:- Saturn
East:- Neptune (mag. +8.0 - second half of month)

Deep Sky
Naked eye / binoculars:-
Melotte 111 - Mel 111 - The Coma Star Cluster (Open Cluster)
Messier 44 - M44 - The Praesepe (Open Cluster)

Telescopes:-
Messier 67 - M67 - Open Cluster
Messier 51 - M51 - The Whirlpool Galaxy (Spiral Galaxy)
Messier 97 - M97 - The Owl Nebula (Planetary Nebula)
Messier 101 - M101 - The Pinwheel Galaxy (Spiral Galaxy)
Messier 65 – M65 – Spiral Galaxy
Messier 66 - M66 - Intermediate Spiral Galaxy
Messier 95 - M95 - Barred Spiral Galaxy
Messier 96 - M96 - Intermediate Spiral Galaxy
NGC 4244 - Spiral Galaxy
NGC 4565 - Needle Galaxy - Spiral Galaxy

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