Australian Sky & Telescope - June 2018

http://www.skyandtelescope.com.au 53

SThe Dumbbell Nebula looks like a well-

gnawed apple core through the eyepiece.

Upping the magniication may reveal

extensions more evocative of an AFL football.

Dumbbell Nebula

DUMBBELL NEBULA: WESTVIEW OBSERVATORY / CC BY-SA 4.0; GREAT HERCULES CLU

STER: SERGIO KAMINSKY. NASA, ESA, AND C. ROBERT O’DELL

(VANDERBILT UNIVERSITY). ESO

The stunning Ring Nebula, M57, positively

glows in this Hubble Space Telescope image.

Ring Nebula

WTheOmega,orSwan,Nebula(M57)isawinterdeepskydelightinSagittarius.

Omega Nebula

in Scorpius. It was a faint daub of light

to the unaided eye when I sketched this

lovely pile of jewels with my 130-mm

refractor at 48×. Its brightest star is the

irregular variable BM Sco, which looks

yellow-orange through the telescope.

Its magnitude range is about 5.3 to 6.5.

While a sketch can’t compare to a nice

personal view or photo, it gives a good

idea of the relative brightness of the

stars. The Butterfly Cluster is so named

because many of its stars seem to

outline four wings, with perhaps even

a head and antennae to the northwest.

Can you picture the lepidopteran?

„ Contributing Editor SUE FRENCH

welcomes your comments at scfrench@

nycap.rr.com.

channel within, like a shadowy bay

lapping on a silver shore. In a fairly

dark sky, this emission nebula is readily

visible to the unaided eye as a misty

patch hovering above the brightest stars

of Sagittarius. My sketch shows the

view through my 130-mm refractor at

48 ×. No filter was used when placing

the stars, but a narrowband filter was

added to help define the nebula. The

ebony lagoon divides the nebulosity

enveloping the open cluster NGC 6530

from the section harboring the brilliant

but tiny double-knot of nebulosity

called the Hourglass. The two sections

are crowned by fainter bands of mist to

their north. The brightest star within

the nebula is blue-white 9 Sagittarii,

and just off M8’s western side, the star

7 Sagittarii shines pale yellow.

Another captivating nebula in

Sagittarius that begs for a sketch is the

Omega Nebula (M17), though I’ve

always preferred its alternate nickname,

the Swan Nebula. One look at its most

prominent feature brings to mind a

celestial swan floating on the dark

waters of the night. Beyond the figure

of the swan, large swaths of diaphanous

haze wrap around the swan’s body. An

O III or a narrowband filter makes the

nebula stand out better, and each was

used to refine the nebulosity on my

sketch. Surrounded by its full retinue

of stars, the swan is also enchanting

without a filter.

We’ll wind up this issue’s tour with a

drawing of the Butterfly Cluster (M6)