The Caldwell Objects

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ery to be unlikely, I presumed the
glow to be nothing but a spurious
patch of bright Milky Way. Through
the 4-inch NGC 6124 appeared about
⅓ times larger than this "patch,"
which was contained by an obvious
oval-shaped asterism of 9th-to 12thmagnitude
stars. Closer inspection
revealed that that single oval was
comprised of two fainter ovals side
by side, each scintillating with the
light of fainter suns. I checked the
Astronomical Journal, the Astrophysical
Journal, and the Monthly Notices of
the Royal Astronomical Society but
did not find a reference to this
"cluster." Apparently no modern
research has been done
on it or the surrounding field. The situation
remained at a standstill until the year 2000, when
Brent Archinal revised the cluster's size from 29'
to 40'. When I plotted his position for the cluster's
center (provided in the table below) and placed a
circular 45'-diameter template around it, I was
pleased to discover that the new dimensions
included this curious patch of dim starlight and
the bright ovals of stars. But why, then, did I see
two distinct "clusters"?
The answer may be simple. On National
Geographic Society - Palomar Observatory Sky
Survey prints I noticed an almost perfect semicircle
of darkness (open to the northeast) slicing
through the cluster's northeastern quadrant, just
where I saw one cluster ending and the other
beginning. This dark semicircle outlines the
southwestern edge of the large oval of stars I
detected in binoculars. Of course, the other
possibility is that there really is just a random
patch of Milky Way here. Check this object out
and decide for yourself. The reason NGC 6124
looks so large and diffuse is because it is relatively
nearby (1,530 light-years). If NGC 6124
298
indeed spans 40', then its true physical diameter
is 18 light-years.
I find that NGC 6124 looks best in binoculars.
At a glance it is a circular object with a dense
10' core. With time, though, the core begins to
break up. Soon it's a mottled haze with
prominent clumps of stars to the northeast,
southwest, and east. Particularly absent is any
notable mottling to the west. So the cluster looks
somewhat like an arrowhead pointing eastward.
At 23x in the 4-inch a pair of parallel and slightly
curving bands of stars (oriented northwestsoutheast)
flows through the center of the
cluster's densest part. Look for a tiny gang of
knitted suns at the northwestern end of the core,
between these two parallel streams. The streams
open out into a delta of darkness at the
southeastern end of the core; look for a
prominent pair of lOth-magnitude suns here.
Christian Luginbuhl and Brian Skiff note that the
densest portion of the cluster contains about 25
stars in an area 6' across. All kinds of pairs and
groupings dapple the cluster. Using my
imagination NGC 6124 looks like the
Deep-Sky Companions: The Caldwell Objects