Sky & Telescope - November 2021 - 55

11th-magnitude winger is 23″ farther
out). Finally, cupping my hands around
the eyepiece to help block out stray
light, I took in the entire field and
counted at least 20 stars down to about
magnitude 11.5. Nice!
I Walk the Line
Returning to Zeta, which lies a tad
north of the celestial equator, I pushed
the Dobsonian westward a little less
than 6° to 3.0-magnitude Alpha (α)
Aquarii, barely south of the equator
line. Yellowy Alpha guards a noticeably
reddish, 8.4-magnitude star 13′ northwest.
Of greater interest to me was the
tight tandem Σ2862, which anchors
the eastern end of a ½°-wide triangle
1° north-northeast of Alpha. The 8.0and
8.4-magnitude stars, 2.5″ apart,
resolved cleanly at 120×.
After Alpha & Co., I swept 8° west
to M2. This showpiece globular cluster
hangs farther south of the equator than
Alpha, though not by much. If you're
using an equatorial mount, simply
place Alpha north of center in a low37
+4°
PEGASUS
3
4
5
6
7
8
9
Σ2909
η
BU1515
BU77
ζ
γ
Sadachbia
ο
-2°
α
Sadalmelik
BU1212
M2
32
25
+2°
π
Σ2862
CHE316
24
Σ2809
0°
Σ2817
power eyepiece, then shift westward in
right ascension until you scoop up the
6.6-magnitude prize. This smooth move
also works with an alt-az Dob, provided
Alpha and M2 are near the meridian.
The Aquarius globular sits just inside
a 17′-wide triangle formed by three
10th-magnitude stars. Two of them, 14′
apart, flank the cluster. Images show
M2 almost bridging those flankers, but
in my city-based optics at 48×, M2 is a
diffuse, unresolved sphere that at best
is 3′ across. No wonder - its leading
members are magnitude 13.1, while
most of the rest of the cluster's stars are
at least three steps fainter. Regardless,
the hazy hive invited a closer look.
Doubling to 96× produced a strongly
concentrated, grainy ball. Its tenuous
halo faded imperceptibly into space.
I spotted a solitary sun immediately
east of the halo, though in reality the
cluster spreads well beyond that star.
At 169×, M2 seemed slightly elliptical
with a brilliant, distinctly grainy core.
And I saw stars in the halo. Indeed, at
218× the halo was salted all over with
pinpoints. The pale outskirts expanded
when I again cupped my hands around
the eyepiece and stared patiently using
averted vision. M2 spanned 6′ - a
captivating sight though still not quite
half the object's full size.
I trained my smaller scopes on M2
and hoped for the best. In my 180-mm
Mak-Cass at 84×, I beheld a respectable
globular - obviously prominent,
especially toward the center, and softly
speckled at the edge. My adjacent
solitary sun was also clearly visible. At
113× I detected starlike glints in the
halo, and likewise, the cluster's broad
middle was teasingly granular. The view
exceeded my expectations.
M2 was a tougher challenge for
my 120-mm apochromatic refractor.
Working at 38×, the apo presented a
luminous but minuscule object. The
tiny-shiny blob demanded higher
magnification, so I applied 129×. M2
morphed into a nebulous sphere that
was impressively bright at its center, and
my averted vision caught subtle mottling
of the halo. I boldly upped the apo
AQUARIUS
-4°
κ
51
22h 40m
22h 30m
22h 20m
22h 10m
22h 00m
21h 50m
21h 40m
Sadalsuud
β
21h 30m
WALKING THE LINE A stroll along the celestial equator in Aquarius takes us from 3.6-magnitude Zeta Aquarii past 2.9-magnitude Alpha Aquarii to
6.6-magnitude globular cluster M2 - a span of 14º. Within that expanse are several interesting double stars and one of the sky's finest globulars.
sk yand tele scope .o r g * NOVEMBER 2021 55
Star magnitudes

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Sky & Telescope - November 2021

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