Sky & Telescope - January 2020 - 56

JANUARY 2020 OBSERVING
Deep-Sky Wonders

p Open cluster Stock 8, together with the surrounding emission nebula IC 417, is visible in
small telescopes under moderately dark skies.
u Sharpless 2-237 is so bright that it almost hides NGC 1931, its embedded star cluster.

the primary. The sparse cluster shows
11 stars and is elongated north-south
about 6½′, while the nebula is a little
longer and extends farther east of the
cluster than west.
Stock 8 looks much richer when
viewed through my 10-inch reflector at
118×. I see 35 to 40 moderately bright
stars loosely strewn across 11′ of sky. IC
417 engulfs the more crowded regions
of the cluster and covers about 8′.
Viewed through my little refractor
at 47×, IC 417 shares the field with
the smaller but much more obvious

nebula Sharpless 2-237. The 11thmagnitude star nestled in its heart is
almost overpowered by the glow of the
nebula, but it shows up much better
when I increase the power to 87×. It
sits at the northwest corner of a 3½′
box that it forms with three dimmer
stars. The nebula is very bright close to
its star and fades sharply outward to a
diameter of perhaps 3½′.
NGC 1931, the cluster associated
with Sh 2-237, begins to emerge in my
10-inch scope at high power. The bright
star is shown to be a quadruple, with

the three brightest members arranged
in a tiny triangle and the fourth
component to their northeast. Several
additional stars straggle south through
west-southwest of the group.
The three clusters highlighted here
are among the youngest visible in the
sky. Their eldest members are a mere 4
million years old, and starbirth within
them is still ongoing.
¢ Contributing Editor SUE FRENCH
wrote this column for the January 2010
issue of Sky & Telescope.

Chariot of Stars, Clouds of Fire
Melotte 31
IC 410 / NGC 1893
Espin 332
AE Aurigae
IC 405
Cheshire Cat
Stock 8 / IC 417
Sh 2-237 / NGC 1931

Type

Mag(v)

Size/Sep

+33° 22′

5h 22.6m

+33° 22′

14.8″

5h

21.4m

+33° 23′

5h

16.3 m

+34° 18′

Asterism

-

135′

7.0

40′ × 30′

8.9, 9.5

Dec.

18.2m

Nebula / cluster
Double star

RA
5h

Bright Star

6

-

Bright nebula

-

30′ × 20′

5h 16.6m

+34° 25′

Asterism

3.9

90′

5h 27.3m

+34° 52′

Cluster / nebula

-

15′

5h 28.1m

+34° 25′

7′

5h

+34° 15′

Nebula / cluster

-

31.4m

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.

56

JANUARY 2 02 0 * SK Y & TELESCOPE

IC 417: SE A N WA LK ER / S&T; NGC 1931: M ASIL IM AGING TE A M

Object



Sky & Telescope - January 2020

Table of Contents for the Digital Edition of Sky & Telescope - January 2020

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