Sky and Telescope - October 2015 - 35

Phi (φ) Pegasi. On the west side of the trio, NGC 7769,
displaying a circular halo around a luminous core, is
the brightest in the group. NGC 7771 appears nearly as
bright but is more elongated with a bright bar-shaped
central feature. I have detected the pair in a 5-inch
telescope. NGC 7770 is in contact with 7771 but is much
more difficult to see, appearing as a very faint nebulous
spot surrounding a stellar nucleus.
A similar trio featuring a bright pair with a faint
companion lies 1° northwest of Alpha Pegasi and about
2.5′ from an 8th-magnitude field star, HD 217602, that
interferes just a bit with observations. The brightest
in the group is NGC 7465, a luminous oval halo that
intensifies toward its center. Northwest of NGC 7465 is
the rather elongated spiral, NGC 7463, a thin, uniformly
bright stripe of light. Its faint companion, NGC 7464, is
the dimmest and most difficult to observe of the group.

Hickson 93

TYC 1715-1334-1
7553
NGC 7549

7547

7550

Hickson Groups

NGC 7771 Trio

7558

JOSEF PÖPSEL / STEFAN BINNEWIES

Canadian astronomer Paul Hickson compiled a list of 100
compact galaxy groups in 1982. These so-called Hickson
Groups of four or more closely associated galaxies often
show interaction among members. Favorite targets of
amateur astronomers, many of the groups are quite challenging and often appear as no more than faintly detectable, undifferentiated blobs at low or moderate power. Yet
some of the groups can be separated into their individual
members even with 10 inches of aperture.
Pegasus contains seven Hickson groups. One of the
more accessible is Hickson 93 (also cataloged as Arp 99)
in the southwest corner of the Great Square. NGC 7550,
the largest and brightest member, shows as distinctly
round with a vivid core. Look for two stars, magnitude 6.5 and 6.7, about 1.5° apart; NGC 7550 is midway

REACHING OUT The twisting arms of NGC 7549 contrast with the
compact spirals of its companion galaxies, as shown in this LRGB composite taken with an f/8 60-cm Hypergraph in secondary focus.

+19° 15′

HD 219293

7769

HD 219186

PEGASUS

Hickson 93
7553

7770

7549

+19° 00′

7547
7558

TYC 1715-1948-1

7550

Star magnitudes

7771

TYC 1715-1334-1

GALACTIC CIRRUS. Ken Crawford's LRGB composite,
taken with a 20-inch f/8.3 Ritchey-Chrétien Cassegrain,
shows the trio cloaked in a thin cloud of interstellar dust.
+18° 45′ 23h 16m

23h 15m

9
10
11
12
13

23h 14m

Sk yandTelescope.com October 2015

35



http://www.SkyandTelescope.com

Sky and Telescope - October 2015

Table of Contents for the Digital Edition of Sky and Telescope - October 2015

Contents
Sky and Telescope - October 2015 - Cover1
Sky and Telescope - October 2015 - Cover2
Sky and Telescope - October 2015 - 1
Sky and Telescope - October 2015 - Contents
Sky and Telescope - October 2015 - 3
Sky and Telescope - October 2015 - A
Sky and Telescope - October 2015 - B
Sky and Telescope - October 2015 - 4
Sky and Telescope - October 2015 - 5
Sky and Telescope - October 2015 - 6
Sky and Telescope - October 2015 - 7
Sky and Telescope - October 2015 - 8
Sky and Telescope - October 2015 - 9
Sky and Telescope - October 2015 - 10
Sky and Telescope - October 2015 - 11
Sky and Telescope - October 2015 - 12
Sky and Telescope - October 2015 - 13
Sky and Telescope - October 2015 - 14
Sky and Telescope - October 2015 - 15
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Sky and Telescope - October 2015 - 17
Sky and Telescope - October 2015 - 18
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Sky and Telescope - October 2015 - 35
Sky and Telescope - October 2015 - 36
Sky and Telescope - October 2015 - 37
Sky and Telescope - October 2015 - 38
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Sky and Telescope - October 2015 - 40
Sky and Telescope - October 2015 - 41
Sky and Telescope - October 2015 - 42
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Sky and Telescope - October 2015 - Cover3
Sky and Telescope - October 2015 - Cover4
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