2019-07-01_Australian_Sky_&_Telescope

54 AUSTRALIAN SKY & TELESCOPE July 2019

wears a yellow-orange hue. Two stars

smolder orange: one in the southeastern

edge, and another of similar brightness

8 ′ south-southwest of the cluster’s

centre. Besides the colour, number and

diversity of its stars, M25 holds another

charm — a cute little D of seven faint

stars rests at its heart.

Pointing the 130-mm scope to

the bright double star 5 Aquilae, the

granular haze of Berkeley 79 shares the

field of view and sports one faint star

at 37×. At 117× four dim stars emerge:

three in a southward-pointing triangle

and one to its east. The northwestern

triangle star looks elongated at this

Beyond the NGCs

Object Const. Mag(v) Size/Sep RA Dec.

Dolidze 27 Oph 6.3 25 ′ 16 h36.5m –08° 56 ′

Collinder 316 Sco 3.4 105 ′ 16 h55.5m –40° 49 ′

Trumpler 24 Sco 8.6 60 ′ 16 h55.8m –40° 43 ′

Trumpler 26 Oph 9.5 7 ′ 17 h28.5m –29° 30 ′

IC 4665 Oph 4.2 70 ′ 17 h46.2m +05° 43 ′

Dolidze-Dzim 9 Her 6.2 34 ′ 18 h08.8m +31° 32 ′

Messier 25 Sgr 4.6 30 ′ 18 h31.8m –19° 07 ′

Berkeley 79 Aql — 10 ′ 18 h45.0m – 01° 09 ′

Stephenson 1 Lyr 3.8 40 ′ 18 h54.5m +36° 54 ′

Angular sizes and separations are from recent catalogues.Visually,anobject’ssizeis oftensmallerthan

the catalogued value and varies according to the apertureandmagnificationoftheviewinginstrument.

Right ascension and declination are for equinox 2000.0.

power, but going to 164× proves it to

be a pair. Some extremely faint stars

also pop into view. Through the 25 cm

at 68×, I see a fairly large patch of mist

sprinkled with very faint stars, and

5 Aquilae exposes three components

in a little arc. At 187× Berkeley 79

reluctantly surrenders a central clump

of 10 stars plus perhaps 20 corralled

into a 10′ halo around it. Berkeley

clusters debuted in a two-part, 1962

paper by Arthur Setteducati and Harold

Weaver of the University of California,

Berkeley.

We’ll finish our tour with

Stephenson 1, the fetching splash of

stars surrounding Delta^2 (δ^2 ) Lyrae.

This orange star pins thecluster’sheart

and offers a pretty contrastwithbluish-

white Delta^1 to the west-northwest.

About 30 to 40 mixed brightandfaint

stars embellish a patch ofskyat least

½° across. The group wasproposedas

a possible cluster in a 1959paperby

Charles Stephenson.

Although some of theseclustersmay

ultimately prove to be mereasterismsof

unrelated stars, stargazersusuallyjudge

their worth by how interestingthey

appear. I hope a few of themwillcatch

your attention and add bitofvarietyto

your observations of theskywelove.

¢ This is SUE FRENCH’sfinalTargets

column. She would like tothank

everyone for the kind farewells,andshe

hopes to meet you underthestars.

A line drawn from

Omicron(ο) Sgrto

Xi^2 (ξ^2 ) Sgrpoints

towardM25.Under

magnification,the

openclusterreveals

anabundanceof

colourfulstars.

pTop: The 6th-magnitude star5 Aquilae

shares a field of view with thesomewhatdim

Berkeley 79, which resemblesa meekpile

of caster sugar through theeyepiece.More

aperture and higher magnificationreveals

individual stars. Look for thecentralgathering

of about a dozen suns. Above:Manyofus

have probably looked at Stephenson1 without

realising it was a star cluster.Theorange

Delta^2 Lyrae, which shines atthecluster’s

centre, is surrounded by 30to 40 starsasdim

as 9th magnitude. Blue-whiteDelta^1 is alsoa

cluster member.

M25

5 Aql

Berkeley 79

Sagittarius Stephenson 1

ξ^2

ο

δ^2 Lyr

δ^1 Lyr

M25 SAGITTARIUS: STEPHEN RAHN / PUBLIC DOMAIN; BERKELEY 79 & STEPHENSON 1: POSS II / CALTECH / STSCI / PALOMAR OBSERVATORY

μ

λ

ε

TARGETS by Sue French