2019-07-01_Australian_Sky_&_Telescope

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CR 316 AND TR 24: MICHAEL A. COVINGTON; IC 4665: BOB FRANKE; DODZ 9: POSS II / CALTECH / STSCI / PALOMAR OBSERVATORY

IC 4665 is centred1.3°north-northeast

ofyellow-orangeBeta(β) Ophiuchi.

Seenthroughthe105-mmscopeat

28 ×, it’sa loosebutobviousbunch

ofstars7thmagnitudeandfainter.

About 22 starsoccupythemainbunch,

whichspans 40 ′. Starswrappedmore

sparselyaroundthosedoublethecount

andextendtheclustertoa diameter

of 70 ′. My25-cmscopeat 43×reveals

a mixtureof 60 brightandfaintstars

spatteredacross 45 ′. Thebrightestpose

inoddlydeliberate-lookinglines,arcs

andgeometricshapes.Thecluster’sIC

designationspringsfromthesecond

IndexCatalogue, a supplementtothe

NewGeneralCatalogue.

Dolidze-Dzimselejsvili 9 is a pretty

aggregationoflooselystrewnstars

perched 40 ′westoftheorangestar 104

Herculis.Itscoordinatesdifferfrom

sourcetosource,butvisuallyit seems

tolieat thoseinthetable.Throughthe

105-mmscopeat 17×, about 25 stars,

8thmagnitudeandfainter,assemblein

a ½°collectionwidelyframedbythree

brightfieldstars.Manyclustermembers

roughlyoutlinea five-pointedstarwith

itscentrenearlybarrenandmostofits

southeasternpointsnappedoff.At 36 ×

about 40 starsbedeckthegroup,some

colourful.Thebrightpairinthenorth

shinesyellow-orangeandpaleyellow.

Thedimmerstarofa similarpairsouth

ofcentreglowsyellow-orange,asdo

themiddlestarina lineofthreetoits

westanda brightstarnearthecluster’s

northwesternedge.

The 11 Dolidze-Dzimselejsviliobjects

appearedina 1966Astronomicheskii

TsirkulyarpaperbyMadonaDolidze

andGalinaJimsheleishvili,a better

transliteration of the second author’s

name than the one commonly adopted

in catalogues.

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

colourful stars. The brightest one in the

northeast glows yellow-orange, and the

one in the northwest gleams yellow. The

luminous star just east of centre shines

yellow, and the next brightest to its east

tThe region near Zeta^1 and Zeta^2 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.

qLeft: 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 centre.

Tr 24

Scorpius

IC 4665 DoDz 9

Cr 316

NGC 6231

ζ^2 ζ^1