Sky & Telescope - September 2021 - 35

ALAN DYER
O
n summer evenings, Cygnus, the Swan, soars high
overhead, winging its way along the hazy band of the
Milky Way toward the galactic center. The constellation
is full of bright star fields, hazy nebulae, and numerous
clusters that help reveal something of the structure of our
home galaxy.
This is the fifth binocular tour in our series. Previously we
explored the Milky Way from Canis Major to Hydra (S&T:
Dec. 2015, p. 32); Monoceros to Gemini (S&T: Mar. 2017,
p. 30); Perseus to Auriga (S&T: Jan. 2018, p. 60); and, most
recently, Cepheus to Cassiopeia (S&T: Oct. 2019, p. 28). Now
it's time to delve into the Cygnus Milky Way.
I made my observations with 15×70 binoculars, which
have a true field of view of 4.4°. But I expect most targets
included here will be visible in smaller binoculars with magnifications
in the 7× to 10× range. A rich-field telescope, such
as a small reflector or short-tube refractor, would also work
well for these Cygnus targets. Indeed, I often find a small
scope is helpful for confirming my binocular sightings, or
for follow-up observing sessions. So, grab your favorite starcatcher
and let's take wing.
Getting Oriented
Before taking up optics, spend a moment to admire Cygnus
with your unaided eyes. The first thing that jumps out is the
distinctive Northern Cross asterism with its long axis formed
by Alpha (α) Cygni (Deneb), Gamma (γ) Cygni (Sadr), and
Beta (β) Cygni (Albireo), and the cross piece marked by Delta
(δ) and Epsilon (ε) Cygni. Now imagine the cross is a southflying
swan and note the pleasing symmetry of its wings,
with Iota (ι) and Zeta (ζ) Cygni as the northwestern and
southeastern wingtips, respectively.
Finally, check out the wide, naked-eye doubles in the trailing
edges of the wings: Omicron1 (ο1) and Omicron2 (ο2)
Cygni in the northwestern wing, and Sigma (σ) and Tau (τ)
Cygni in the southeastern wing. The stars in both pairs are
nearly equally bright, and when they're oriented horizontally
in the sky, they seem to stare back like pairs of spooky eyes!
Let's start our binocular exploration at the head of the
Swan, with the alluring double star Albireo. Some of you will
already have noticed that I've singled out this star for special
treatment as September's Binocular Highlight on page 43.
I'm using Albireo as the jumping-off point for our tour, so
when you're ready to move on, consult the star chart on page
36 and scan northeast along the axis of the constellation
to Eta (η) Cygni. About 3° east-northeast of Eta you'll find
28 Cygni and a pair of curious star chains that arc southwards
to a set of open clusters. The western arc leads to NGC
6871, while the eastern arc terminates with NGC 6883 and
Biurakan 2. None of these objects stands out distinctly from
STREAM OF STARLIGHT Given its large size and prime location in
the heart of the summer Milky Way, Cygnus is, perhaps surprisingly,
home to only two Messier objects: M29 and M39. However, for the careful
binocular observer there are many additional delights, including faint
nebulae, double stars, and a host of lesser-known open clusters.
sk yand tele scope .o r g * SEPTEMBER 2021 35
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Sky & Telescope - September 2021

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