Sky & Telescope - September 2020 - 65

parts must be the sides and the darkish parts the ends of a
marginally elliptical nebula whose major axis, to my eye, was
leaning northwest. Wrong! I was off by 90° - images show
the annulus leaning northeast. Also, the disk is more strongly
elliptical in photographs than the hollowed-out "snowball" I
examined visually. Appearances can be deceiving. The bright
northeast and southwest portions I saw mark the ends, not
the sides, of the elongated structure.
So, my characterization of NGC 7662 as a mini-Ring
wasn't quite correct. True, both objects are elliptical, and
they share similar orientations (their major axes are tipped
approximately 45°). However, while M57 displays the
expected shiny sides and dusky ends, NGC 7662 does the
opposite. My bias toward bright sides caused an optical illusion that fooled me completely.
Each observer registers their own impression. Admiring NGC 7662 later in a 20-inch f/4 Dobsonian at 406×
(unﬁltered), I sensed the annular ring was gently rippled, or
scalloped, all around the edge. The scope's owner commented
that, to him, the Snowball "looked like a rose." It was a deeply
appealing description. A Blue Rose, anyone?

Ghostly Galaxy

p RINGS IN THE SKY The Blue Snowball Nebula (NGC 7662, left) and
the Ring Nebula (M57) present elliptical shapes of similar orientation on
the sky. But while M57 exhibits bright sides, NGC 7662 displays bright
ends. These images aren't to the same scale.

69× registered a slender wisp only half as long, captured in
a 5′-wide triangle of 11th-magnitude stars. My at-the-ocular
comment was "a willowy tendril in an attractive setting."
Stars were everywhere. I noted a 14th-magnitude pinprick
off the galaxy's southern tip and a 12th-magnitude star 6½′
farther south. Another 11th-magnitude star glimmered a few
arcminutes off the galaxy's northern tip.
Changing to my ultra-wide 158× eyepiece resulted in
NGC 7640 extending (as images conﬁrm) a bit outside the
triangle mentioned above. The galaxy was curiously asymmetrical, the northern third slightly outshining its southern counterpart. Averted vision came to the rescue again, as it helped
me trace the extent of that thin southern ﬂank. The central
hub was obvious, but I saw no dark line of dust bisecting it
(though images do conﬁrm a dust lane). A faint star overlaid
the galaxy immediately southeast of the hub. Several dimmer
stars were superimposed over the whole splotchy, misty mass.
Increasing the magniﬁcation to 228× stretched NGC 7640
an additional arcminute in each direction, but the pallid
subject was becoming very dim at that power. Excellent sky
conditions and a patient eye are required to fully appreciate

M ASIL IM AGING (2)

My ﬁnal stop in the Andromeda Outback was NGC 7640, a
two-armed, barred spiral galaxy around 30 million light-years
from Earth. The 11.3-magnitude edge-on system is located
a mere 1.8° south-southwest of the Blue Snowball. Finding
the galaxy would be a piece of cake, right? Wrong again. At
the time, my chosen area of sky was skirting the zenith (the
dreaded "Dobby Hole"), and with so many stars crowding my
reversed-image, right-angle ﬁnderscope, I could easily miss
the prize - and I did!
Consulting my best charts, I settled on a simple star-hop
beginning at 13 And, which had guided me earlier. From
that star, an imaginary arrow shoots southwestward past
NGC 7662 and through the orangey 6th-magnitude variable
star V385 Andromedae, grazing the southern tip of NGC 7640.
Employing a wide-ﬁeld
eyepiece yielding 69×, I made
a slow sweep toward the
Delights in Andromeda's
galaxy until I encountered a
nebulous feather. No wonder
Object
Type
Mag(v)
I missed it the ﬁrst time. The
object's surface brightness is
very low - 14.4 magnitudes
per square arcminute -
which conspires against any
quick catch.
NGC 7640 is oriented
essentially north-south
in a busy starﬁeld on the
periphery of the Milky Way.
In photographs, the galaxy
is a generous 12′ × 2′ in size;
however, my telescope at

Outback
Size/Sep

Dec.

NGC 7686

Open cluster

5.6

15′

23h 30.1m

+49° 08′

NGC 7662

Planetary nebula

8.3

29″ × 26″

23h 25.9m

+42° 32′

NGC 7640

Spiral galaxy

11.3

12′ × 2′

Struve 2985

Double star

7.2, 8.0

15.7″

23h 10.0m

+47° 58′

Struve 3034

Double star

7.7, 9.9

5.7″

23h 44.5m

+46° 23′

Struve 3004

Double star

6.3, 10.1

13.5″

23h 20.7m

+44° 07′

7.5″

23h

+44° 04′

Struve 2973

Double star

6.4, 10.1

23h

22.1m

+40° 51′

02.8m

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.

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Sky & Telescope - September 2020

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