The Caldwell Objects

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but stars or at least to contain stars and to give
"every other indication of consisting of stars
entirely." With their modest instruments, today's
amateurs can understand why Herschel made the
assumptions he did. For example, when viewing
NGC 7331 through a 6-inch telescope, Christian
Luginbuhl and Brian Skiff detected a stellar
nucleus and grainy texture within the disk.
Increasing the aperture to 10 inches, they report,
brought out increased mottling, especially in the
inner halo, and two 13.5-magnitude stars west of
the northern tip of the disk. Herschel, with his
much larger instruments and very high
magnifications, must have detected these
features, among others, and he may well have
envisioned something akin to a distant cluster,
perhaps one like M4 in Scorpius, whose center is
a needle of starlight.
Through the Genesis at 23x NGC 7331 is
wonderfully apparent as a small, elongated form
nestled in a rich field of stars. With averted
vision I perceive a tight lens-shaped core
surrounded by a dim, elliptical outer halo or
shell. At 72x and above, the galaxy becomes a
complex mottled glow. Its nucleus appears
especially sharp and is surrounded by fleeting
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shadows of dust. My drawing shows a great
amount of detail, which becomes visible over
several hours of continuous observing. With time,
the galaxy's mottled disk transforms into a clearly
discernible spiral pattern with intermittent dust
lanes, the most prominent being the western
furrow. Most impressive, however, is that some of
the mottling within the bright arms corresponds
to true patches of stars or ΗII regions. One
prominent region appears just northwest of an
approximately 12th-mag-nitude star lying eastsoutheast
of the lens-shaped core.
NGC 7331 is haunted by several faint companions,
four of which appear close to its western
edge. I say haunted because, at 72x in the 4-inch,
these companions seem to pop dimly into view
with averted vision, only to vanish under a direct
gaze. The brightest companion, NGC 7335, is
listed in The Deep Sky Field Guide at magnitude
13.3, though I wonder if it is not brighter; I blindly
(and correctly) positioned the tiny fuzz ball in my
original sketch, which I made at the eyepiece, and
wondered in the margin if it was really a galaxy.
Luginbuhl and Skiff detected two more
companions, NGC 7337 (magnitude 14.4) and
NGC 7340 (magnitude 13.7), with a 10-inch
telescope. The fourth, NGC 7336, apparentiy was
too difficult for them. The Deep Sky Field Guide lists
it at magnitude 15.8, but Sky & Telescope's Roger
W Sinnott . notes that this galaxy may not be so
faint; the Lyon-Meudon Extragalactic Database, he
says, attributes a blue magnitude of 15.4 to NGC
7336, and it probably is a little brighter visually.
About ½° south-southwest of NGC 7331,
scrunched into a mere 3.5' of sky, are the five
challenging galaxies collectively known as
Stephan's Quintet: NGC 7317, NGC 7318A, NGC
7318B, NGC 7319, and NGC 7320. Stephan's
Quintet is of continual interest to astronomers. A
1995 study shows that radio emission from
Deep-Sky Companions: The Caldwell Objects