Sky & Telescope - June 2019 - 55

CR 316 A ND TR 24: MICH A EL A . COVINGTON; IC 46 65: BOB FR A NK E;
DODZ 9: POSS II / CA LTECH / STSCI / PA LO M A R OBSERVATORY

the hub star is a nice double, and I can
pick out 20 stars in a 7′ gathering with
indeﬁnite borders.
Much farther north in Ophiuchus,
IC 4665 is centered 1.3° north-northeast of yellow-orange Beta (β) Ophiuchi. Seen through the 105-mm scope
at 28×, it's a loose but obvious bunch
of stars 7th magnitude and fainter.
About 22 stars occupy the main bunch,
which spans 40′. Stars wrapped more
sparsely around those double the count
and extend the cluster to a diameter
of 70′. My 10-inch scope at 43× reveals
a mixture of 60 bright and faint stars
spattered across 45′. The brightest pose
in oddly deliberate-looking lines, arcs,
and geometric shapes. The cluster's IC
designation springs from the second
Index Catalogue, a supplement to the
New General Catalogue.
Dolidze-Dzimselejsvili 9 is a pretty
aggregation of loosely strewn stars
perched 40′ west of the orange star 104
Herculis. Its coordinates differ from
source to source, but visually it seems
to lie at those in the table. Through the
105-mm scope at 17×, about 25 stars,
8th magnitude and fainter, assemble in
a ½° collection widely framed by three

t The region near Zeta1 and Zeta2 Scorpii
makes for good observing. The tight open
cluster NGC 6231 shines almost directly north
of the stars, while the overlapping clusters
Trumpler 24 and Collinder 316 stretch to the
northeast. Together, these objects combine to
mimic a comet, with NGC 6231 or the Zetas
forming its head and Trumpler 24 and Collinder
316 shaping an imaginary tail. Deep-sky images reveal the emission nebula IC 4628, which
envelopes Trumpler 24.

Scorpius

Tr 24
Cr 316

NGC 6231

ζ2

ζ1

bright ﬁeld stars. Many cluster members
roughly outline a ﬁve-pointed star with
its center nearly barren and most of its
southeastern point snapped off. At 36×
about 40 stars bedeck the group, some
colorful. The bright pair in the north
shines yellow-orange and pale yellow.
The dimmer star of a similar pair south
of center glows yellow-orange, as do
the middle star in a line of three to its
west and a bright star near the cluster's
northwestern edge.

The 11 Dolidze-Dzimselejsvili objects
appeared in a 1966 Astronomicheskii
Tsirkulyar paper by Madona Dolidze
and Galina Jimsheleishvili, a better
transliteration of the second author's
name than the one commonly adopted
in catalogs.
Although discovered by Jean-Philippe
Loys de Chéseaux circa 1745-46,
Messier 25 wasn't included in the New
General Catalogue, which gives me an
excellent excuse to include this spectacular cluster in our non-NGC tour.
My latest visit to M25 was with the
105-mm scope. At 36× this 30′ beauty
ﬂaunts 55 mixed bright and faint stars
displayed in arms ﬂung out in all directions. It also boasts several colorful
stars. The brightest one in the northeast
glows yellow-orange, and the one in the

q Left: IC 4665 forms an obvious grouping 1.3º north-northeast of Beta Ophiuchi. Despite being an easy sight to see, it wasn't included in either
Messier's lists or the NGC. In fact, it wasn't even included in the 1895 update to the NGC, the Index Catalogue (IC), but had to wait until the second IC
was issued in 1908. Right: The open cluster DoDz 9 lies 40′ west of 104 Herculis. Look for the two yellow-orange star pairs, one at the cluster's north,
one south of center.

IC 4665

DoDz 9

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Sky & Telescope - June 2019

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