The Caldwell Objects

71
71
NGC 2477
Type: Open Cluster
Con: Puppis
RA: 07 h 52.2 m
Dec: -38° 32'
Mag: 5.8
Diam: 20'
Dist: 3,700 light-years
Disc: Abbé Nicolas Louis de Lacaille, listed in his
1755
catalog
J. H ERSCHEL: Superb cluster, [gradually brighter
toward the middle], 20' diameter, much more than fills the
whole field. Stars [of] 10 [th] and 11th [magnitude] all nearly
equal, (h 3103)
NGC 2477 IN P UPPIS IS A GLORIOUS OPEN
cluster full of subtle detail that should quench the
visual thirst of all observers. I listed it as the fifth
of "Twenty spectacular non-Messier objects" in
Deep-Sky Companions: The Messier Objects. The
cluster is easy to find. Look 11° southeast of the
Greater Dog's tail star, 2nd-magnitude Eta (η)
Canis Majoris, and just 2½° northwest of 2ndmagnitude
Zeta (ζ) Puppis. But be careful,
because our target is also 1½° southeast of the
spectacular magnitude-2.8 open cluster NGC
2451. Together NGC 2477 and NGC 2451
constitute one of the most stunning open-cluster
pairs in the heavens. Barbara Wilson calls them
the "southern M46 and 47." "What is so strange,"
Wilson says, "is that NGC 2477 and 2451 are
visible at the same time [and] in the same
constellation as M46 and 47 yet so few people
know about them. Stranger yet is that NGC 2477
is brighter, at magnitude 5.8, than M46 is at
magnitude 6.1; it just lacks a planetary to show
off. [The 11th-magnitude planetary nebula NGC
2438 is
GC/NGC: Remarkable, cluster, bright, rich in stars,
large, little compressed, a star of 12th magnitude.
superposed on M46.] But NGC 2477 is a richer
cluster. I guess it suffers from latitude sickness."
What a catchy phrase, "latitude sickness." But it's
true. If you live on the north 45th parallel, NGC
2477 can rise no more than 6½° above your
southern horizon. Toss in some light pollution
and it's a goner. That's why the Winter Star Party
is so popular with northerners, for it enables
them to dip their telescope tubes deep into
Puppis, where these clusters shimmer in all their
glory.
The 18th century was a golden age for exploring
the far-southern skies. Abbe Nicolas
Louis de Lacaille (1713-62) discovered NGC 2477
during an expedition to the Cape of Good Hope
in southern Africa. From April 19, 1751, to March
8, 1753, Lacaille cataloged, among other things,
42 "nebulae." His list was by no means complete,
though it did suggest what could be
accomplished by sweeping the southern heavens
with an eye open for nebulous objects. Lacaille
placed his discoveries into three classes: "nebulae
without stars" (Class I);
184 Deep-Sky Companions: The Caldwell Objects