56 September 2014 sky & telescopeOBSERVING
Deep-Sky WondersThe Theban Swan
Cygnus is alive with celestial treasures.
Lo, how th’ obsequious Wind, and swelling Air
The Theban Swan do’s upwards bear
Into the Walks of Clouds, where he do’s play,
And with extended Wings opens his liquid way!
— Abraham Cowley, The Praise of Pindar, circa 1645Cowley’s praise of the ancient Greek poet Pindar imitates
an ode by the Roman poet Horace, who lived four centu-
ries after Pindar. In Cowley’s poem the swan is Pindar of
Thebes, yet we might imagine this passage applying to
the constellation Cygnus as well. Gazing at Cygnus we see
heaven’s swan, his wings extended, as he glides along the
celestial river of the Milky Way.
For someone with a small telescope that off ers a very
wide fi eld of view, one of the fi nest sights in Cygnus is the
North America Nebula (NGC 7000). In a 3.6°° fi eld at 17×
with an O III fi lter, my 105-mm refractor shows off all of
NGC 7000, as well as its neighbor the Pelican Nebula, as
shown in the sketch below.
With a 2.7° fi eld at 23×, my 130-mm refractor encom-
passes only one nebula at a time, but the view is: Wow!
With this scope I prefer a narrowband fi lter, which reveals a
wealth of subtle and not-so-subtle brightness vari-
ations within North America. Giving the
scope a westward nudge centers the
Pelican Nebula, which displays
the distinctive shape of its head
and the dark opening of the
beak. The three IC 5068
nebulae are visible south
of the Pelican. The west-
ern one is the most obvi-
ous, the middle one a
fair bit dimmer, and the
eastern one quite faint.
An O III fi lter helps
defi ne the IC 5068 trio a
little bit better, and the
Pelican to a lesser extent.
This fi lter greatly enhances
the contrast between NGC7000 and the surrounding sky, but it almost overwhelms
the more delicate nuances within the nebula. It also
diminishes the luster of the countless stars that beautify
the scene. Yet you might fi nd it necessary if your sky is
more light-polluted than mine.
Best seen without a fi lter, a few star clusters adorn
North America. NGC 6997 is a rich dusting of faint to
very faint stars where you’d expect to fi nd West Virginia.
In northern Canada, NGC 6996 is a portion of the Milky
Way enisled by dark nebulae. The combo is charmingly
called the Dark Ring Nebula or Birds’ Nest, with NGC
6996 as a clutch of eggs in the southern part of the nest.
Boosting the power to 48×, I see Collinder 428, some-
where in the western states, as a 13′ group of 15 stars plus
a detached group of six to the east. A gold 7th-magnitude
star is parked on the cluster’s eastern edge. With my
15-inch refl ector at 221×, the little-known possible open
cluster Teut sch 22 appears in Arizona as a tight little
gathering of a dozen faint to extremely faint stars about
2.6′ across. A 10.7-magnitude star pins its west-southwest-
ern verge, and a 6.8-magnitude star sits 4.4′ north.
Next we’ll visit the planetary nebula NGC 6884, which
lies 37′ west-southwest of golden Omicron^1 (ο^1 )
Cygni. My 130-mm refractor at 102× reveals
a tiny, blue-green disk that doesn’t
seem as sharp as the stars. A 12th-
magnitude star watches over NGC
6884 from 1.7′ west-northwest.
At 164× the planetary doesn’t
look quite as colorful, but
it displays a nice little disk
with a fainter fringe.
Planetary-nebula
distances are notoriously
diffi cult to ascertain, but
a study by Letizia Stang-
hellini and Misha Hay-
wood (Astrophysical Journal,
2010) places NGC 6884 at
14,560 light-years away from
us, plus or minus 20%.
Another obscure open clus-
ter hovers 4.4° north of Omicron^2
Cygni, this one visible in a small
telescope. Alessi-Teutsch 11 is a 26′,The author sketched the North America
and Pelican nebulae as they appear through
her 105-mm scope at 17× with an O III fi lter.DSW layout.indd 56 6/23/14 12:17 PM