The Caldwell Objects

timates, making it 2 billion years younger than
the "best-fit" age for NGC 5286 (Caldwell 84).
At high power look for a filigreed arm extending
southeastward from the outer rim of the central
condensation, and for a prominent arc of 13th- to
14th-magnitude stars on the south side of the
cluster's halo. The latter is separated from the
main disk by a curving dark rift. Overall, the
entire cluster is riddled with rifts, as if it's in the
process of being blown apart. The most
prominent rift (which rivals the one in M2 in
Aquarius) appears in the cluster's northwestern
quadrant, just beyond the outer rim of the central
blaze. It runs from northeast to southwest. The
stars on this rift's northern side taper off to a
point, making it appear as if the cluster is
wearing some kind of fashionable hat. I find the
cluster's multitude of dark lanes as interesting as
any of its other features. (Unfortunately they are
not visible in most photographs, ours included,
because those photographs tend to overexpose
the cluster's inner zones.) Be sure to spend much
time looking at NGC 1261 with averted vision
while playing with the focus knob. Some nicely
resolved stars reside in the globular's outer halo.
Under averted vision, many of these stars snap
into view before fading into the background mist.
In this way, the cluster takes on the appear-
87
ance of a busy beehive. While traveling in Tacna,
Peru, Barbara Wilson observed NGC 1261 with a
7-inch f/5.1 reflector and found the cluster to
have "an extremely bright little nucleus and
fuzzy edges. A few stars are seen but not many,
the core is not stellar. . . . Amazing to semiresolve
this cluster with a 7-inch!" And with his
12-inch reflector Ernst Hartung commented that
this "well condensed" globular resolves into
"crowded stars right to the centre. It is about 2.5'
and the scattered outliers do not extend far; the
stars are however very faint and hard to detect
with [an 8-inch] although the cluster looks
granular."
Each of NGC 1261's constituent stars has 1 / 2
as much iron as does our Sun, making the cluster
moderately metal rich as globulars go, especially
since it resides in our galaxy's halo. Its spectral
type is F7. Since the globular is away from the
plane of the galaxy, our sightline to it is virtually
free from annoying interstellar dust. Images
taken with large telescopes show some very
small and dim galaxies on the cluster's immediate
outskirts. Noteworthy among them are an openfaced
spiral about 4.5' to the south-southeast of
the cluster's core; an edge-on galaxy about 5.5' to
the south; and a fantastic pair of possibly
interacting galaxies about 5.0' to the southsouthwest,
along a line to a roughly 13thmagnitude
sun. The cores of all these galaxies,
save for the edge-on one, are apparent in images
from the Digitized Sky Survey (one of which
appears on page 345). These galaxies are not
plotted on the Millennium Star Atlas. What's the
smallest aperture that will show them to an
observer at the eyepiece?
Small-telescope users should be sure to look
for one particular Y-shaped asterism of 10th- and
11th-magnitude stars, like a dim version of M73,
just 35' to the southeast of NGC 1261. Asterisms
of this type are fairly common; keep your eyes
peeled for them.
The Caldwell Objects 347