58 ASTRONOMY
small telescopes — thus the nebula’s apparent
crescent shape.
One of Cygnus’ most celebrated emission and
ref lection nebulae mirrors the naked-eye splendor
of the Swan’s union of dark and light. The Cocoon
Nebula (IC 5146) lies in a stunning cul-de-sac of
dark nebulosity that connects to a longer, 1° strip
of celestial asphalt. Collectively known as Barnard
168, this extensive inky swath is one of the north-
ern sky’s most visually stunning dark nebulae —
whether with the naked eye, binoculars, or
low-power telescopes. The Cocoon itself appears as
a 10'-wide circular glow almost overpowered by a
pair of roughly magnitude 9.5 stars embedded
within the open cluster Collinder 470.Showing off
Open star clusters abound in Cygnus, but only
a couple are celestial show-offs. Nearly 10° east-
northeast of Deneb we find M39, the Swan’s pre-
mier open cluster, at least in terms of brightness.
Just visible to the unaided eye under a dark sky,
this magnitude 4.5 cluster is a loose collection of
30 suns that belongs to a class of poorly populated
open clusters. Handheld binoculars will easily
resolve about a dozen stars in an area of sky the
size of the Full Moon. The true beauty of the clus-
ter lies in the near-uniform brightness of its most
prominent members, which shine with diamond
blue purity.
Another popular target, M29, appears as a tiny
and tight knot of fuzzy starlight about 2° south-
southeast of Gamma (γ) Cygni. Telescopically, the
magnitude 6.5 cluster transforms into a collection
of about a dozen obvious suns veiled by dusty fila-
ments that mar an otherwise opulent stream of
milky starlight. The brightest of these stars form a
boxy pattern reminiscent of a miniature Pegasus.
NGC 6819, sometimes called the Fox Head
Cluster, is one of the Swan’s silent wonders, a
celestial butterf ly lost in the stellar madness of
the Milky Way, about 2¾° north-northwest of
15 Cygni. Although it’s a magnitude fainter than
M29, it sports some 900 stars in an area 5' across;
many of the brightest stars share similar bright-
nesses, so the cluster stands out especially well at
high powers. At low magnifications, NGC 6819
looks like a shaken snow globe. High powers bring
out a lazy V-shaped pattern of stars (the Fox’s face)
with a knot of dim suns around a prominent dou-
ble near its southern apex (the Fox’s nose).
Now treat yourself to an open cluster illusion.Often overlooked by
celestial observers, open
cluster NGC 6819 makes
a brilliant sight in small
telescopes. BERNHARD HUBL
Smaller than M39 but
an attractive open cluster
nonetheless, M29 lies near
the bright star Sadr (Gamma
[γ] Cygni). RICHARD HAMMAR
Sometimes called
the Smoke Ring Cluster,
NGC 6811 packs 250 stars
into an area half the
diameter of the Full Moon.
ANTHONY AYIOMAMITIS