Neptune, the eighth planet from the Sun and the Solar System's most distant reaches opposition on August 27, 2013. On this date it will be 28.9729 AU (approx. 4334.3 million km or 2693.2 million miles) from Earth and visible all night; rising above the eastern horizon at sunset and then setting in the west as the Sun again rises in the east. With an apparent magnitude of +7.8, it will also be at its brightest for the year.

Even when at it's brightest Neptune is not visible to the naked eye. It's the only planet that requires optical aid to be seen, although Uranus requires dark skies to be glimpsed. However, provided you know exactly where to look, Neptune is a relatively easy binocular and small telescope target.

Neptune as imaged by the Hubble Space Telescope in 1998 (NASA, L. Sromovsky, P. Fry (University of Wisconsin-Madison))

Locating Neptune

Aquarius is a faint zodiac constellation with its brightest stars being of only 3rd magnitude. Neptune is currently moving retrograde and positioned almost exactly bang in the middle of the constellation, about 1 degree to the west of star Sigma Aquarii (σ Aqr - mag. +4.8). Located about 30 degrees NE of Neptune is the "Square of Pegasus" and about 20 degrees SE of Neptune is the brightest star in the surrounding region; Fomalhaut (α Psc) at magnitude +1.2.

The finder chart below shows the position of Neptune amongst the stars of Aquarius on August 27, 2013. Since its distant, it moves relatively little with respect to the background stars, hence the chart is not only valid at opposition but for many days later.

Neptune is currently better situated for observation from the tropics or southern hemisphere, where it appears higher in the sky, compared to northern latitudes.

Neptune Opposition Finder Chart - August 27, 2013

Neptune Opposition Finder Chart - August 27, 2013 - pdf format

Neptune Opposition Data Table

DateAugust 27, 2013
Right Ascension22hr 23m 41.9s
Declination-10d 45m 56.5s
Apparent Magnitude+7.8
Apparent Size2.4"
Illumination (%)100.0
Distance from Earth (AU)28.9729

Sky Highlights - July 2017

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for July

Meteor Shower
Southern Delta Aquariids (Aquarids) meteor shower peaks on July 29

Northern Hemisphere
West:- Mercury (mag. -0.5 to +0.3) (second half of month)
Southwest:- Jupiter (mag. -2.0)
South:- Saturn (mag. +0.2)
West:- Jupiter
South:- Saturn
East:- Neptune (mag. +7.8)
Southwest:- Saturn
South:- Neptune
Southeast:- Uranus (mag. +5.8)
East:- Venus (mag. -4.1)

Southern Hemisphere
West:- Mercury (second half of month)
Northwest:- Jupiter
East:- Saturn
West:- Jupiter
North:- Saturn
East:- Neptune
West:- Saturn
North:- Neptune
Northeast:- Venus, Uranus

Deep Sky

Small telescopes:-
Messier 13 - M13 - Great Hercules Globular Cluster
Messier 92 - M92 - Globular Cluster
Messier 11 - M11 - The Wild Duck Cluster (Open Cluster)
Messier 7 - M7 - The Ptolemy Cluster (Open Cluster)
Messier 6 - M6 - The Butterfly Cluster (Open Cluster)
Messier 4 - M4 - Globular Cluster
Messier 8 - M8 - Lagoon Nebula (Emission Nebula)
Messier 16 - M16 - Eagle Nebula (Emission Nebula with Open Cluster)
Messier 20 - M20 - Trifid Nebula (Emission and Reflection Nebula)

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