http://www.skyandtelescope.com.au 61catalogue of 629 “clusters and
nebulae”. Only 211 of his 629
objects were subsequently spotted
by Sir John Herschel, who observed
from the Cape between 1834 and
1838 using an 18.5-inch speculum
reflector. Half of Dunlop’s 629
objects turned out to be faint
double stars that he was unable to
resolve with his poor-quality, home-
made instrument.
From Lacaille and Dunlop’s lists,
we have selected 10 open clusters
and 10 globular clusters that stand
out for their sparkling beauty.
The list includes objects which
beginners will readily locate as well
as others of fainter magnitudes that
are slightly more difficult.
Open clusters
The following open star clusters
are all south of declination minus
20 degrees — putting them below
the horizon or low in the sky for
observers in Paris, which is why
they did not make it into Messier’s
catalogue.
NGC 2477: Discovered by
Lacaille, this is a very rich,
magnitude-5.8 open cluster of
faint stars with a line of brighter
stars to the northeast. James
Dunlop described it as “a pretty
large faint nebula, easily resolvable
into small stars, or rather a cluster of
very small stars, with a small faint
nebula near the north preceding side,
which is rather difficult to resolve
into exceedingly small stars...” The
magnitude-4.5 star QZ Pup is 20 ́
southeast of the 15-arcminute-
diameter cluster, which is 4,000
light-years away.
NGC 2516: Also discovered
by Lacaille, its bright scattered
stars are only 1,350 light-years
away and cover an area 25 ́ in
diameter. At magnitude 3.8 it is
easily seen with the naked eye at
the foot of the False Cross. Dunlop
described it as a “Very fine cluster
about 35 ́ diameter, many of the
stars of the 6th and 7th magnitude,
mixed magnitudes. Figure irregular
branched.” Through 20 × 80
binoculars, it looks somewhat like
a camel with its legs towards the
False Cross.
NGC 3114: This magnitude-4.2,
snail-shaped open cluster is 3,000
light-years away. With a diameter
of 35 ́, its scattered stars are
superimposed on a bright part
of the Milky Way. Dunlop found
it and saw “A beautiful cluster of
stars, arranged in curvilinear lines
intersecting each other, about 40’
diameter...”
NGC 3293: Only 5 ́ across and
very distant at 7,630 light-years, the
colourful stars in the Gem Cluster
shine with a total magnitude
of 4.7. Dunlop saw “A ve r y s m a l l
cluster of very small bright stars;
round figure, about 4 ́ diameter; rich
in extremely small stars resembling
faint nebula”. The star Eta Carinae
is 1.9 degrees away.
NGC 3532: Lacaille found
this one, with Dunlop describing
it as “a very large cluster of stars
about the 9th magnitude, with a
red star of the 7–8th magnitude,
north following (NW) the centre
of the cluster. Elliptical figure: the
stars are pretty regularly scattered.”
This large (50 ́ diameter) naked-
eye, magnitude-3.0 open cluster
is less than 1,600 light-years away.
John Herschel wrote “It is the most
brilliant object of the kind I have ever
seen.” A black ‘arrow’ runs through
it. The nebula NGC 3581/82 is 2.7
degrees away.
NGC 3766: Lacaille discovered
this magnitude-5.3 open cluster.
Dunlop wrote, “A pretty large cluster
of stars of mixed magnitudes, about
10 ́ diameter. The greater number
of the stars are of a pale white
colour. There is a red star near the
preceding side...” The cluster is 5,700
light-years away and appears as a
saxophone shape. The nebula IC
2944/48 is 1.9 degrees away.NGC 4755: John Herschel
compared this open cluster to a
“superb piece of fancy jewelry”.
At magnitude 4.2, 10 ́ in diameter
and 6,500 light-years away, Lacaille
discovered it with his ½-inch
refractor. Dunlop saw “five stars
of the 7th magnitude, forming a
triangular figure, and a star of the
9th magnitude between the second
and third, with a multitude of very
small stars on the south side.”
NGC 6067: Dunlop discovered
this open cluster, describing it as
“a pretty large cluster of small stars
of mixed magnitudes, about 12 ́
diameter; the stars are considerably
congregated towards the centre,
extended south preceding (SW) and
north following (NE).” At magnitude
5.6, the cluster is 4,650 light-years
away and 15’ across.
NGC 6231: Giovanni Battista
Hodierna found this open cluster
from Ragusa, Sicily in the 1650s.
This brilliant magnitude-2.6
cluster is 4,100 light-years away
and 15 ́ across. Dunlop saw “a
cluster of pretty bright stars of mixed
small magnitudes, considerablycongregated to the centre, about 10 ́
diameter, with a large branch of very
small stars extended on the north
side.” The nebula IC 4628 is about
1.5 degrees away.
NGC 6242: This open cluster
is magnitude 6.4, 3,700 light-years
distant and 9 ́ in diameter. Lacaille
found it and Dunlop described
“a cluster...of small stars, about 4 ́
diameter, with branches extendingNicolas-Louis de
Lacaille (left) and
James Dunlop
were early
cataloguers of the
southern sky.