Sky & Telescope - July 2023 - 55

GARY SERONIK
Star magnitudes
I love the Coathanger nickname;
the modern-day moniker is delightfully
appropriate. Ten stars of 5th to 7th
magnitude convincingly delineate the
familiar shape of a household hanger.
Hanging Around
The effect in my 10×50 binoculars is
striking - a horizontal bar formed by
six stars in a remarkably straight, 1½°long
row, running almost precisely eastwest,
plus four additional stars outlining
the angular hook. It really is a perfect
coathanger. That said, Northern Hemisphere
binocular observers will notice
that the silly thing is upside-down.
Ah, but the Coathanger appears
right-side up in my straight-through
8×50 finderscope - and remains
upright (albeit backwards) when I
use a 90° diagonal on the refractor.
The scope frames the entire asterism
beautifully in a single field of view,
provided I employ (as with Albireo) very
low magnification. At 30×, five of the
stars in the row-of-six shine blue-white,
while the westernmost sparkle is yellow-orange.
The four-star hook offers
two bluish dots and two of a distinctly
warmer hue.
Dominating the Coathanger's hook
is 5.2-magnitude 4 Vulpeculae, the
asterism's leading light. Yellowish 4 Vul
is a triple system listed in the Washington
Double Star Catalog as HJ 2871. The
dependable WDS lists a 10.0-magnitude
companion 13.5″ east of 4 Vul, but
I'm not certain I've glimpsed it in my
120-mm apo, even at 200×. The other
member of the trio lies 50.9″ southwest
of 4 Vul. Alas, this wider star also
eluded me, flickering feebly at magnitude
11.7 - right at the limit of my
modest scope laboring under a soupy
city sky. (I can, however, pick up both
companions of 4 Vul if I use my 10-inch
f/6 Newtonian reflector at 218×.)
Only ¼° northeast of 4 Vul, is
5.8-magnitude HD 182955 (it has no
Flamsteed number). This K5 orange
giant anchors a loose quintuple array
known as Struve (Σ) 2521. Four of the
attendants shine at about magnitude
10.5 - faint but doable, while the fifth
star is well out of reach of my suburban
apo. One attendant (star
B) is 29.0″ north-northeast
of the primary,
another (C) is 75.1″
north-northwest,
and the third (D) is
152.1″ east-northeast.
The apo captures
the spread-out
threesome at 100×,
though 200× pulls in
the group much more
clearly. I chuckle at the irony
of using 200× while observing the
sprawling Coathanger!
Outside the Hanger
Let's explore the area around the
Coathanger. A line from Σ2521 through
4 Vul, extended 1¼° southwestward,
crosses the border into Sagitta where
it passes an L-shaped trio of stars. The
most prominent point in the little L is
a double star called Σ2504. Comprising
7.0- and 9.0-magnitude components
8.7″ apart, Σ2504 unveils its binary
nature at 38×.
One degree north of the Coathanger
is a picturesque region dominated by
19h 35m
19h 30m
VULPECULA
HLM 23
+21°
Σ2540
+20°
Pair
Pair West
East
7
6802
Σ2521
4
U
Σ2504
+19°
SAGITTA
5
4
6
7
8
9
10
AN UPSIDE-DOWN COATHANGER A lovely little arrangement of 5th- to 7th-magnitude stars
known as the Coathanger is located almost 8° southwest of Albireo. For mid-northern observers,
the Coathanger hangs high in the south (albeit upside-down) all summer long.
sk yand tele scope .o r g * JULY 2023 55
5
Brocchi's
Cluster
Cr 399
Σ2523
OPTICAL ILLUSION? Albireo
in Cygnus is arguably the
loveliest double star in the
northern heavens. However,
it's likely not a true
binary system. Although
the two stars appear
close together in our
scopes, according to
results from the Earthorbiting
Gaia astrometry
mission, the bright orange
sun is 330 light-years away,
while the dimmer blue star is
at a distance of 390 light-years.
two stars. The 7.2- and 8.0-magnitude
markers lie 4.1′ apart on a northwestsoutheast
slant. The northwestern star
is Σ2523, a headlight binary whose 8.0and
8.1-magnitude elements, 6.4″ apart,
are a slender split at 38×. The southeastern
star is single, but directly south of
it is a double called HLM 23. HLM must
stand for Horribly Low Magnitude,
because the stars weigh in at 10.5 and
11.0. Fortunately, they're separated by
17.0″ and resolve well at 56×.
The east end of the Coathanger's
horizontal bar is established by
6.3-magnitude 7 Vulpeculae. Just
19h 25m
19h 20m
1
1
19h 15m

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Sky & Telescope - July 2023

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