Sky & Telescope - USA (2019-09)

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SEPTEMBER 2019 OBSERVING
Deep-Sky Wonders

56 SEPTEMBER 2019 • SKY & TELESCOPE

Fox Hunt

Object Type Mag(v) Size/Sep RA Dec. MSA PSA

Alpha (α) Vul Double star 4.4, 5.8 7.1′ 19 h 28.7m +24° 40′ 119 6 6 4

NGC 6800 Open cluster — 15 ′ 19 h 27.1m +25° 08′ (1196) 64

NGC 6793 Open cluster — 7 ′ core, 18′ halo 19 h 23.2m +22° 08′ (1196) (65)

h886 Double star 10.5, 11.5 8.2′′ 19 h 23.22m +22° 09.9′ (1196) (65)

Collinder 399 Asterism 3.6 90 ′ 19 h 26.2m +20° 06′ 1220 6 4

NGC 6802 Open cluster 8.8 5.0′ 19 h 30.6m +20° 16′ 1220 6 4

Stock 1 Open cluster 5.2 34 ′ core, 80′ halo 19 h 35.8m +25° 10′ 119 6 6 4

Σ 2548 Double star 8.5, 9.9 9.4′′ 19 h 36.5m +25° 00′ 119 6 (6 4)

LDN 810 Dark nebula — 18 ′ × 9 ′ 19 h 45.6m +27° 57′ (1172) (64)

Angular sizes and separations are from recent catalogs. Visually, an object’s size is often smaller than the cataloged value and varies according to the aperture and

magnifi cation of the viewing instrument. Right ascension and declination are for equinox 2000.0. The columns headed MSA and PSA give the appropriate chart

numbers in the Millennium Star Atlas and Sky & Telescope’s Pocket Sky Atlas, respectively. Chart numbers in parentheses indicate that the object is not plotted.

NGC 6802 is a beautiful diamond-dust

cluster rich in faint and very faint stars.

It lies at an estimated distance of about

7,000 light-years, and it’s dimmed by

intervening dark clouds that seem to

split the softly shining band of Milky

Way in this area of the sky.

Now let’s move 1.7° east-northeast

of Alpha to Stock 1. Through my

4.1-inch scope at 17×, this is a large,

loose cluster of 20 moderately bright

and many very faint stars. An 8th-

magnitude star sits at the heart of a

core group measuring 30′ × 20 ′. This,

in turn, is surrounded by a 1.4° halo

of stars, mostly encircling the east-

ern half of the core. A reddish orange

star adorns the western reaches of the

cluster. Stock 1 contains many double

stars. The brightest is Σ 2548 , located 14′

southeast of the cluster’s central star.

Its 8.5- and 9.9-magnitude components

can be split at about 50×. A recent study

indicates that most of this cluster’s

true members are roughly concentrated

within the core group’s ½° diameter.

Our fi nal stop will be the dark

nebula LDN 810, which I like to call the

Coalman. The simplest way to fi nd it is

to scan 3.3° due east from Albireo, the

beautiful gold-and-blue double star that

marks the head of Cygnus, the Swan.

With my 10-inch scope at 68×, I see a

north-south oval of inky darkness con-

taining only a few extremely faint stars.

A slightly less conspicuous dark oval

perched atop it turns the nebula into

a fi lled-in 8 or the negative image of a

snowman. The southern patch is about

9 ′ × 6 ′ and the northern one 6′ × 5 ′.

These are just a few of the foxy resi-

dents of Vulpecula. In the October 2006

issue, this tour continues with more

vulpine delights, including the constel-

lation’s brightest planetary nebula and

its fi nest cluster.

¢ Contributing Editor SUE FRENCH

penned this column for the September

2006 issue of Sky & Telescope.

pThe author sees the dark nebula LDN 810 as the negative image of a snowman and thus calls it

the Coalman.