NGC 891 is a tenth magnitude unbarred spiral galaxy located in Andromeda. Also known as the Silver Sliver, it's one of the best examples of an edge-on galaxy in the sky, although a challenging object for small scopes. Due to its attractiveness and scientific appeal, NGC 891 was selected on October 12, 2005 to be the first light image of the Large Binocular Telescope at Mount Graham International Observatory in Arizona. In 2012, it was again selected as first light image, this time for the Discovery Channel Telescope (DCT) Large Monolithic Imager at the Lowell Observatory in Happy Jack, Arizona.

The Silver Sliver was discovered by William Herschel on October 6, 1784 and is best seen from the Northern Hemisphere during October, November and December. Astronomers think that our Milky Way galaxy would look remarkably similar if viewed edge-on.

NGC 891 (credit:- NASA, ESA, and The Hubble Heritage Team (STScI/AURA))

Finder Chart for NGC 891 (credit:- freestarcharts)

Finder Chart for NGC 891 - pdf format (credit:- freestarcharts)

The Silver Sliver is located in eastern Andromeda close to the Perseus border. It's positioned 3.5 degrees east of beautiful double star Almach (γ And - mag. +2.1) with naked-eye open cluster M34 (mag. +5.5) a further 3.5 degrees eastwards, in Perseus.

At mag. +10.0, NGC 891 is a difficult small telescope object. From a dark site it's possible to spot it with a small 80mm (3.1 inch) scope but only as a faint thin slither of light. However, for most observers a larger scope is required. A 200mm (8-inch) instrument shows a thin needle of nebulosity with a bright central core. On nights of good seeing a narrow dust lane bisecting the galaxy's long axis can be seen. Large amateur scopes show variations in the dust band with many foreground stars populating the view. Whatever type of instrument you're using, the best views of this object require dark skies with magnifications greater than 100x recommended. In total, NGC 891 covers 13.5 x 2.5 arc minutes of apparent sky.

The Silver Sliver is number 23 in the Caldwell catalogue. It's about 30 million light-years distant and has an actual diameter of 120,000 light-years. The galaxy is estimated to contain about 500 billion stars and is the dominant member of the NGC 1023 group of galaxies, which also includes NGC 1023, NGC 925, NGC 1058, NGC 1239 and many other smaller dwarf galaxies.

On August 21, 1986, a supernova (SN 1986J) that peaked at mag. +14 was discovered in NGC 891.

NGC 891 Data Table

NGC891
Caldwell23
NameSilver Sliver
Object TypeUnbarred Spiral Galaxy
ClassificationSA(s)b
ConstellationAndromeda
Distance (ly)30 Million
Apparent Mag.10.0
RA (J2000)02h 22m 33s
DEC (J2000)42d 21m 03s
Apparent Size (arc mins)13.5 x 2.5
Radius (light-years)60,000
Number of Stars500 Billion
Notable FeatureMember of the NGC 1023 group of galaxies

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

Southern Hemisphere
Evening
West:- Mercury (second half of month)
Northwest:- Jupiter
East:- Saturn
Midnight
West:- Jupiter
North:- Saturn
East:- Neptune
Morning
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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