Sky & Telescope - July 2023 - 56

ALAN DYER
JULY 2023 OBSERVING
Suburban Stargazer
CY G N U S
Albireo
HANGING AROUND Buried in the Vulpecula
Milky Way, the Coathanger asterism, also
known as Collinder 399, is an eye-catching
splotch of glitter in a country sky. Even amid
city lights, Cr 399 looks great in binoculars.
1 ° further east are two dim doubles,
/3
aligned east-west, within 10′ of each
other. They're not listed in the comprehensive
Washington Double Star
Catalog, so I'm dubbing them Pair West
and Pair East. The former comprises
9.1- and 10.0-magnitude stars separated
by 47″, while the latter has 9.8- and
11.3-magnitude stars 33″ apart. Both
pairs show well at 100×.
There's more. Slightly below the two
pairs is NGC 6802, an 8.8-magnitude
open cluster. Only 5′ across, NGC 6802
claims approximately 200 members,
none brighter than 14th magnitude.
This is one tough target for suburban
scopes, but with averted vision I can
detect it at 100×. On the best nights,
it's a grainy bit of coathanger fluff sharing
the high-power field with my West
and East doubles.
We'll complete our tour with the
challenging double star, Σ2540, a touch
more than ½° beyond Pair East. Formed
by 7.5- and 9.2-magnitude pinpoints
a scant 5.4″ apart, Σ2540 wins my
seldom appreciated, frequently ignored
Itty-Bitty Binary award (Coathanger
category). The delicate duo resolves
beautifully at 100× in the refractor.
Hooked Yet?
The binocular-friendly Coathanger
is definitely worth inspecting with a
telescope. If, like me, you observe from
a badly light-polluted city, you can nail
everything I've described above, with the
possible exception of open cluster NGC
6802. If your sky is better than mine,
even that tiny bit of coathanger fluff
might hang nicely in your eyepiece, too.
¢ Contributing Editor KEN HEWITTWHITE
has never actually traced out the
constellation Vulpecula in the night sky.
56 JULY 2023 * SKY & TELESCOPE
V U L PE CU L A
Anser
Cr 399
Coathanger Collection
Object
Type
Cr 399
Albireo
4 Vul AB
4 Vul AC
Σ2521AB
Σ2521AC
Σ2521AD
Σ2504
Σ2523
HLM 23
Pair West
Pair East
NGC 6802
Σ2540
Asterism
Double star
Double star
Double star
Double star
Double star
Double star
Double star
Double star
Double star
Double star
Double star
Open cluster
Double star
Mag(v)
3.6
3.2, 4.7
5.2, 10.0
5.2, 11.7
5.8, 10.5
5.8, 10.5
5.8, 10.6
7.0, 9.0
8.0, 8.1
10.5, 11.0
9.1, 10.0
9.8, 11.3
8.8
7.5, 9.2
Size/Sep
~60′
34.9″
13.5″
50.9″
29.0″
75.1″
152.1″
8.7″
6.4″
17.0″
47.0″
33.3″
5′
5.4″
RA
19h 25.4m
19h 30.7m
19h 25.5m
19h 25.5m
19h 26.5m
19h 26.5m
19h 26.5m
19h 21.0m
19h 26.8m
19h 26.8m
19h 30.2m
19h 30.9m
19h 30.6m
19h 33.3m
Dec.
+20° 11′
+27° 58′
+19° 48′
+19° 48′
+19° 54′
+19° 54′
+19° 54′
+19° 09′
+21° 10′
+21° 10′
+20° 20′
+20° 20′
+20° 16′
+20° 25′
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 magnification of the viewing instrument.
Right ascension and declination are for equinox 2000.0.
Sky & Telescope - July 2023

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