The Caldwell Objects

49 & 50
knot in a vast nebulous ring that entirely surrounded
the cluster." Then his photographs
brought out the entire wreathlike wonder and
earned it the name "Rosette."
Thus, all the NGC pieces of the Rosette
Nebula — 2237, 2238, and 2246 — are but parts of
a single nebular complex. Brent Archinal adds a
strong argument as to why the designation "NGC
2237-9, 46" is incorrect for the Rosette Nebula.
First, NGC 2239 is not, and historically has never
been, part of the nebula. (So references such as
the second edition of Sky Atlas 2000.0 need to be
fixed to reflect that.) Uranometria 2000.0 indicates
that NGC 2239 is a small cluster of stars just westnorthwest
of NGC 2244. Wrong again, says
Archinal, who describes the problem in a Webb
Society monograph, The "Non-Existent" Star
Clusters
198
of the RNGC. NGC 2239 is
in fact the same cluster as
NGC 2244, thanks to a
positional error by John
Herschel. Archinal credits
Canadian amateur Alister
Ling for being the first to
note the discrepancy,
which Ling did in 1992
after considering John
Herschel's 1833
description of this object:
"The place of an 8thmagnitude
star in the
most compact part of a
large, poor, but brilliant
cluster." Ling astutely
noted that there is no 8thmagnitude
star at those
coordinates, but if we add
1 minute to NGC 2239's
putative right ascension,
we find such a star in
NGC 2244. John
Herschel himself apparently caused the confusion,
as Archinal explains: "He first explicitly
states that this object, h 392 (later NGC 2239) is
the same object as [HVII-2] (later NGC 2244) in
his 1833 observations. He also describes no other
such cluster in this region, so it is quite clear that
he is talking about the one and only . . . large
cluster here. But in the [General Catalogue] . . .
he apparently noticed the discrepancy in right
ascension. Instead of recognizing the 1-minuteof-time
error, he assumed h 392 was a new object
and listed these two objects separately, now as
GC 1420 (h 392) and GC 1424 ([HVII-2]). Later
references of course continued to incorrectly list
this new object." In summary, if simplicity is to
rule, the Rosette Nebula's designation should be
NGC 2237-8, 46; the Rosette's central cluster
should be
Deep-Sky Companions: The Caldwell Objects