60 August 2014 sky & telescopeKen Hewitt-White
Going Deep
Dots and Donuts in Aquila
These nine planetary nebulae range from easy to... not so easy.
night a few summers ago, I
issued myself a somewhat arbitrary challenge: select and
observe a variety of planetary nebulae inside the “dia-
mond” of Aquila outlined by alpha (α), zeta (ζ), delta (δ),
and theta (θ) Aquilae. The subsequent fi eldwork was sat-
isfying indeed, as my 17.5-inch f/4.5 Dobsonian revealed a
pleasing range of sizes, shapes, and luminosities among
the nine chosen objects. You might like to give this proj-
ect a try yourself.
I began my tour with the 11.4-magnitude planetary
nebula NGC 6803, located about 3¾°° west-southwest of
the 2.7-magnitude star gamma (γ) Aquilae, also known as
Tarazed. At 83× this planetary appeared starlike and was
fl anked by a 13th-magnitude star 1′ to its south-southwest
and a 10.6-magnitude star almost 3′ to the north. Adding
an O III fi lter dimmed the brighter star and obliterated
the dimmer one, leaving the nebula between them as
the dominant dot. And it was no longer starlike. At 222×,
fi lter removed, the tiny disk appeared bluish.On a dark country Dropping almost 1° southward, I swept up 12.0-mag-
nitude NGC 6804 about ¼° southwest of the 7th-magni-
tude star HD 184061 (SAO 124749). Unfi ltered at 83×, the
66 ′′-wide splotch resembled a fan-tailed comet: its “tail”
being the diff use nebulosity and its “nucleus” a 12.5-mag-
nitude star on the nebula’s northeast edge. My 222× ocu-
lar revealed a fainter star farther northeast, another one
on the west edge of the nebula, plus the 14.3-magnitude
central star — in all, a crooked line of four dim points.
The O III fi lter blunted the stars but produced a disk that
appeared oval and mottled.
Trending farther southward brought me to my teensi-
est target, NGC 6807, less than 1¾° below 4th-magnitude
Mu (μ) Aquilae. In a wide-angle eyepiece generating 83×,
the 12.0-magnitude planetary shared the fi eld with two
attractive stars: the reddish, 6th-magnitude variable V450
Aquilae ¼° to its southwest and the orangey 6.6-mag-
nitude double star Σ2543 ½° on the opposite side of the
planetary. Σ2543’s 10th-magnitude companion is 11′′ from
the primary star.
The nebula itself appeared stellar beside a 10th-
magnitude star 1.5′ northeast. With the fi lter, the nebula
outshone the star and seemed bigger than a pinpoint.
Ramping up to 285× produced a minuscule disk wavering
in the less-than-perfect seeing.
I found NGC 6852 roughly 2° east-northeast of 4th-
magnitude eta (η) Aquilae. At magnitude 12.6, it showed
readily at 83× despite the glare from 7.4-magnitude
HD 189511 (SAO 125338) just 4′ to the planetary’s west-
southwest. Although a respectable 28′′ in size, NGC 6852
appeared tiny at low power, and a 13.2-magnitude star
immediately west-northwest of it imparted a binary-like
eff ect. Increasing the magnifi cation to 285× revealed an
obvious disk with a 14.4-magnitude star near its southeast
edge, a fainter star overlaying the same side, and a starlike
brightening on the northwest edge. Adding an O III fi lter
suppressed the starlight and, to my delight, produced an
unevenly bright ring.
The most appealing specimen that night, 11.4-magni-
tude NGC 6781, was easy to fi nd almost 4° north-north-
west of δ Aquilae and less than ½° east of the 6.7-magni-
tude star HD 180504 (SAO 124457). At lowest power I saw
a 1.5′-wide, doughnut-shaped cloud that was bright across+10°0 °++6852Abell 62PK 44-5.1PK 45-2.1PK 46-3.1αβχδφ
γηιμνοπθστ υωξψ ζ1931AQUILATTAltair675567566760678167906803
6804689120 h 00 m 19 h 40 m 19 h 20 m+5°(^6807) Σ 2497
Star magnitudes
2 3 4 5 6 7