Sky & Telescope - September 2019 - 55

A K IR A FUJII

Deneb

Vega

On September evenings
the prominent Summer
Triangle, comprising the
stellar beacons Vega,
Deneb, and Altair, sparkles amid the Milky Way's
glow. In the accompanying text, Sue French tours
deep-sky objects near
the center of this widefield photograph.

19h 50m

Altair

19h 40m

19h 30m

19h 20m

`

CYGNUS

+28°

LDN 810

3

+26°

10
6800

Σ 2548

Stock 1

8

_
+24°

13

6830

VULPECULA

6823

2

12

6793
Star magnitudes

nestled against an 11.5-magnitude
secondary to the northeast. With my
10-inch scope at 43×, I saw this same
concentration of stars near the center
of a larger and brighter collection with
an 8th-magnitude star at its western
edge. This makes the cluster about 20′
across, embracing 50 mixed bright and
faint stars.
William Herschel obviously cataloged the bigger group. The Catalogue
of Open Cluster Data (2004) lists NGC
6793 as being 18′ across with a 7′ core,
so it seems that references giving a size
of 7′ limit the cluster to the stars of the
more highly condensed core.
Collinder 399 is a striking asterism
commonly known as Brocchi's Cluster or the Coathanger. It has several
stars bright enough to be seen with the
unaided eye in a very dark sky. From
my semi-rural home in upstate New
York, I merely see a nebulous haze 4½°
south of Alpha. Binoculars or a finder
show six stars in a curved bar plus four
more forming a hook to the south.
Since the bar is 1.4° across, seeing the
Coathanger in a telescope requires a
low-power, wide-angle field of view.
Stephan Ruchhöft from northern
Germany reads Sky & Telescope's German edition, Astronomie Heute [Editor's
note: no longer in print]. Stephan wrote
telling me that he "discovered" Collinder 399 while scanning the sky with
binoculars. At the time he was planning
a family trip to the Alps, which inspired
him to see the star figure as a ski lift.
The bar of the Coathanger is the ski
lift's cable, and the hook is its chair.
This inventive image has the advantage over the Coathanger of being seen
right-side up in binoculars by Northern
Hemisphere observers.
Just 18′ off the eastern end of the
Coathanger's bar, we come to the open
cluster NGC 6802. My little refractor
at 28× displays a broad, north-south
band of mist about 5′ tall. A pair of
9th- and 10th-magnitude stars lies
6½′ northwest, and another pair of
10th and 11th magnitude lies the same
distance northeast. A smattering of
extremely faint stars dots the haze at
87×. With my 10-inch reflector at 170×,

+22°

2
3
4
5
6
7
8

6802
9

7

5

Cr 399
(Brocchi's
Cluster)

+20°

4

sk yandtele scope.com * S E P TE M B E R 2 019

55



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Sky & Telescope - September 2019

Table of Contents for the Digital Edition of Sky & Telescope - September 2019

Contents
Sky & Telescope - September 2019 - Cover1
Sky & Telescope - September 2019 - Cover2
Sky & Telescope - September 2019 - 1
Sky & Telescope - September 2019 - Contents
Sky & Telescope - September 2019 - 3
Sky & Telescope - September 2019 - 4
Sky & Telescope - September 2019 - 5
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Sky & Telescope - September 2019 - 7
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