The Caldwell Objects

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But until we have the ability to go back in time
... to peer over [Herschers] shoulder as he was
sweeping, I don't think we'll ever know for sure
exactly what NGC 6882 is."
To find NGC 6885 first use your naked eye
and look about 10° (one fist's width) southwest of
Epsilon (ε) Cygni, the elbow of the celestial
Swan's southern wing, or a similar distance
(actually 9°) east-southeast of Beta (β) Cygni
(Albireo), the famous telescopic double star
marking the Swan's nose. There you will find the
6th-magnitude star 20 Vulpeculae huddled with
two other similarly bright stars (18 Vulpeculae
and 19 Vulpeculae) in a ½°-wide patch of sky; 20
Vulpeculae is the southernmost of the three. Two
Tin-magnitude stars also accompany 19
Vulpeculae, and the entire naked-eye region
looks like a speckled haze about the size of the
full Moon. This haze is not caused by NGC 6885,
which shines below the limit of naked-eye
visibility at magnitude 8.1, but by an optical
effect that spins closely knit stars into webs of
imaginary wispiness. (Messier masters may
prefer to star-hop to 20 Vulpeculae from M27, the
Dumbbell Nebula, about 5° to the southwest.)
I should mention that some references
include 20 Vulpeculae in the cluster's total
brightness. The second edition of Sky Catalogue
2000.0, for instance, lists the cluster's photographic
magnitude as 5.7. But this gives observers
unrealistic expectations. Even under a dark
sky one could easily miss NGC 6885 with a
sweep of 7x35 binoculars because 20 Vulpeculae
overwhelms its dim light, which looks like a burp
of "gas" just southwest of that star. The cluster
might well be lost entirely under city lights.
With the nearly 3° field of the Genesis at 23x,
the region including 18, 19, and 20 Vulpeculae
looks like a cluster being ripped apart by some
unseen tidal stress; the densest popu-
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lation of stars near 20 Vulpeculae is a crumbling
"comet" with a wide parabolic hood of starlight
and a tail that flows northward toward 19
Vulpeculae. Look for a bar of fuzzy starlight 6'
northwest of 20 Vulpeculae, oriented eastnortheast
to west-southwest; this is the concentration
of stars in NGC 6885 that Trumpler
classified as NGC 6882. An obvious trapezoid of
stars appears immediately to the southwest of 20
Vulpeculae.
At 72x a conspicuous pair of stars lies
immediately to the northeast of 20 Vulpeculae,
while a dozen or so fainter suns lie to the east. A
rough line of equally spaced 11th- to 12thmagnitude
stars slice through the fuzzy bar of
light, which contains still fainter suns popping in
and out near the limit of visibility. Doubling the
magnification spreads out the stars farther,
providing the best view of William Herschel's
"cluster of coarsely scattered stars." In total some
35 stars populate the 20'-wide cluster when
counted down to 12th magnitude; 60 members
can be tallied down to 13th magnitude. Other
suns make up the Milky Way backdrop. A nice
l0th-magnitude topaz star lies just to the
northeast of 19 Vulpeculae, itself a red-tinted
type K3I-II giant.
Now return to low power. In a 2° field of
view crisscrossing corridors of darkness can be
seen in the region directly south of NGC 6885.
The view is best if 18 Vulpeculae is placed at the
northern end of the field of view. One corridor
begins at 19 Vulpeculae and ends just east of the
roughly 5th-magnitude variable (and tight
double) star QR Vulpeculae, about 1.5° to the
southeast. Another begins on the western end of
NGC 6885 and ends to the west of QR
Vulpeculae. A third corridor lies farther to the
west and is paralleled by a sharp needle of dark
nebulosity, also to the west. Two perpendicular
dark alleys can also be seen in the southern end
of this field. The challenge is to
Deep-Sky Companions: The Caldwell Objects