The Caldwell Objects

Eta Carinae Nebula. But remember that photographs
of other emission nebulae — Barnard's
Loop, say, or the California Nebula — make
those nebulae appear much brighter than they do
to the eye. I remained unsure of IC 2948's
visibility until I observed Collinder 249 with
binoculars and David Levy's 3½-inch Questar
under dark African skies in lune 2001. The
nebulosity was apparent in both instruments as a
dim fog that swelled into view under averted
vision.
From Hawaii my 4-inch refractor reveals a
quite obvious circular patch of nebulosity (IC
2944) around Lambda Centauri at 23x. Under
averted vision a dim elliptical extension can be
followed to the north, where it encounters a
roughly lOth-magnitude star 7' away. This
observation agrees with Volume 7 of the Webb
Society Deep-Sky Observer's Handbook, which
describes the nebula as "oval... of about 10' to
15' extent, surrounding λ Centauri." I also suspected
the presence of nebulosity around the
brightest stars and star chains to the southeast
100
of Lambda Centauri.
At 72x many pairs of stars can be seen
throughout Collinder 249, which is most strongly
concentrated about 25' southeast of Lambda
Centauri. An obvious U-shaped asterism marks
the chain's southeastern end. (Collinder recorded
the cluster as a "chain of bright stars with
nebulosity.") The cluster's stars then spread out in
two diverging forks to the northwest, each of
which ends at a bright pair of binocular suns. The
beauty of this star chain notwithstanding,
Collinder's suggestion that this cluster is a
Southern Pleiades seems unfounded. My
eyepiece views certainly did not give such an
impression. Perhaps in photographs, where the
cluster's stars are embedded in a complex
network of nebulosity, one could see how
Collinder derived such a name. But I have to
wonder. You see, IC 2602 (Caldwell 102) in
Carina, which lies about 6° southwest of Lambda
Centauri, is popularly known as the Southern
Pleiades. Did Collinder mix up these clusters'
names?
The Caldwell Objects 401