NGC 5694, also known as Caldwell 66, is a faint globular cluster in the constellation Hydra. At mag. +10.2, it's not a bright object and the reason is simply due to its distant. At approx. 114,000 light-years, it's further away than the actual diameter of the Milky Way galaxy. However, despite this it can be spotted with amateur telescopes, although virtually impossible to resolve in most backyard instruments.

William Herschel discovered NGC 5694 on May 22, 1784. Even when using the best telescope of the day, Herschel couldn't resolve it into stars and catalogued it as a faint nebula. The object was first resolved and at the same time its true nature determined by Carl Lampland and Clyde Tombaugh in 1932. Recent measurements suggest that it's moving fast enough to eventually escape the galaxy and move into intergalactic space.

The cluster is best seen from southern and equatorial latitudes during the months of April, May and June.

NGC 5694 (credit:-  NASA, ESA, Hubble Heritage Team (STScI/AURA), Judy Schmidt)

Finder Chart for NGC 5694 (credit:- freestarcharts)

Finder Chart for NGC 5694 - pdf format (credit:- freestarcharts)

NGC 5694 is located in the far eastern part of Hydra, close to the Libra border. Antares, mag. +1.0, the brightest star in Scorpius is positioned 24 degrees east of the globular. NGC 5694 can be spotted with small scopes. A 100mm (4-inch) refractor at 200x magnification reveals a small fuzz, spanning 3.6 arc minutes, that's clearly non-stellar. Through a 250mm (10-inch) reflector, NGC 5694 appears round with a gradual brightening towards the centre. It's not resolvable as the brightest member stars shine at mag. +15.5. A very large 500mm (20-inch) scope will partially resolve the cluster, especially on nights of good seeing and transparency.

NGC 5694 has a spatial diameter of 120 light-years and is estimated to contain 250,000 stars. It's one of a handful of globulars more than 100,000 light-years distant that can be seen with amateur scopes.

NGC 5694 Data Table

NGC5694
Caldwell66
Object TypeGlobular Cluster
ConstellationHydra
Distance (light-years)114,000
Apparent Mag.+10.2
RA (J2000)14h 39m 36s
DEC (J2000)-26d 32m 18s
Apparent Size (arc mins)3.6
Radius (light-years)60
Number of Stars250,000
Notable FeatureOne of the more remote globular clusters of the Milky Way

Sky Highlights - September 2017

Opposition
Neptune reaches opposition on September 5th

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for September

Northern Hemisphere
Evening
West:- Jupiter (mag. -1.7)
Southwest:- Saturn (mag. +0.5)
East:- Neptune (mag. +7.8)
Midnight
South:- Neptune
East:- Uranus (mag. +5.7)
Morning
West:- Neptune
South:- Uranus
East:- Venus (mag. -3.9), Mars (mag. +1.8) (from second week), Mercury (mag. +0.5 to -1.3) (from second week)

Southern Hemisphere
Evening
West:- Jupiter
Northwest:- Saturn
East:- Neptune
Midnight
West:- Saturn
North:- Neptune
Northeast:- Uranus
Morning
West:- Neptune
Northwest:- Uranus
Northeast:- Venus
East:- Mars (end of month)

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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