The Caldwell Objects

very wide double of near-equal intensity, and it
punctuates the cluster's southeastern arm. This
very wide double also forms the eastern half of a
trapezoid along with two slightly dimmer suns,
the southwestern of which is a much tighter
double. The cluster contains no obvious central
condensation, though the χ asterism lies on a
blanket of fainter suns. Since NGC 6025 is large
and scattered, the view is best at low power, but
increasing the magnification to 72x or higher will
bring out some nice star pairings and a Southern
Cross asterism just north of the cluster's visual
"center" — which I see as the center of a C
asterism. It is hard to determine the cluster's full
extent because it is seen against such a rich Milky
Way
95
background. Although most observers see 30
cluster stars out to about 5', Archinal has tallied
139 members out to 15' (11 light-years). The
cluster is about 90 million years old, making it a
contemporary (loosely speaking) of the Pleiades
(M45) in Taurus.
If you return to the 1°-long arc of three 6thmagnitude
suns and move 1° southwest of its
southernmost star, you'll encounter the small,
pale glow of NGC 5979, a magnitude-11.5
planetary nebula less than 25" across. And if you
return to Beta Trianguli Australis and look about
35' to the southeast, you'll find the coppercolored
classical Cepheid S Trianguli Australis,
whose light varies between magnitude 6.1 and
6.8 every 6.32 days.
The Caldwell Objects 383