Sky & Telescope - December 2018 - 55

JIM THOMMES

u It's a short hop from M103 to the bright
sparks of NGC 663. You can spend nights
studying just this part of the sky, with its rich
starfield, several open clusters, and abundance
of dark nebulae.

Star magnitudes

At 102× NGC 663 sports about 50
stars, magnitude 8.5 and fainter. The
cluster's densely starred core spans
8½′, while the sparse, irregular halo
swells the group to 13′. The cluster's
lucida (brightest star) glistens in the
north-northeastern portion of the core.
Despite its B2II spectral type, which
identifies it as a blue-white bright giant,
the star looks yellow-white. Its light is
significantly filtered by intervening dust
in the plane of the Milky Way, lending
the star the yellower cast indicated by
its color index of +0.65. Such a hue is
equivalent to an unfiltered G1V star,
much like our Sun. Struve 153 gleams
1.3′ east of the lucida. This noteworthy
pair presents a 9th-magnitude primary
harboring a 10th-magnitude companion 7.7″ to the east-northeast.
Also perused at 102×, NGC 654
discloses 15 stars, excluding the bright
one at its edge, with the most crowded
region north of the cluster's center.
NGC 659 seems less obvious at this
magnification, showing nine stars magnitude 10.5 and fainter, loosely scattered across an east-west band covering
3½′ × 1½′. Boosting the power to 164×
gives a score of stars to NGC 654 and a
dozen to NGC 659.
NGC 663 is even more appealing in
my 10-inch reflector at 88×. At least 60
stars spangle a patch of sky about ¼°
across, the four brightest shining in
shades of yellow. A cradle of stars cups
the cluster from the south; its brightest
star (SAO 11958) is deeply red-orange.
A somewhat dimmer star 4.2′ southeast
shares the same hue. Adding more color
to the tableau, the bright star off the
cluster's west-northwestern side glows
deep orange. NGC 654 bares 34 stars
within 5¼′, while NGC 659 has 21 stars
straggling across a 4¼′ × 1¾′ band, plus
a few outliers to the south.
The members of our foursome are
youthful open clusters, their ages ranging from about 14 million years for
NGC 654 to 35 million years for NGC

3
4
5
6

2h 30m

2h 00m

1h 00m

559
IC 1805

654
Mrk 6

M103

r
869

0h 00m
+65°

9

g
225

381

136

p2

457

436

+60°

129

a

b

Stock 2

884

Y 3053

CASSIOPEIA

663
659

0h 30m

35

637

¡

7

1h 30m

`

p1

q

d
281

744

_

T

+55°

e

h

+

PERSEUS

c

NGC 654

IC 166

HD 10362
NGC 663

∑153

Berkeley 6

NGC 659

44 Cas

sk yandtelescope.com * DECE MBE R 2 018

55



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Sky & Telescope - December 2018

Table of Contents for the Digital Edition of Sky & Telescope - December 2018

Contents
Sky & Telescope - December 2018 - Cover1
Sky & Telescope - December 2018 - Cover2
Sky & Telescope - December 2018 - 1
Sky & Telescope - December 2018 - Contents
Sky & Telescope - December 2018 - 3
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