M79
ADAM^ BLOCK/NOAO/AURA/NSFWWW.ASTRONOMY.COM 63the stars are and how irregu-
lar M12’s edge appears.
M10 is half a magnitude
fainter than M12 but of simi-
lar size — 15.1' compared
with 14.5' — making each
about half the diameter of the
Full Moon. To find M10, look
8° northeast of Zeta Ophiuchi.
Through a 4-inch tele-
scope, the biggest difference
between M10 and M12 is that
M10’s core appears brighter.
It, too, has a faint halo of
stars. Larger telescopes show
both the halo’s richness and
how its brightness slowly
decreases with distance from
the core.
For our next globular, head
back to Hercules to home in
on its second-brightest glob,
M92. This treat glows at
magnitude 6.5 and measures
11.2' in diameter. You’ll find
it 6° north of Pi (π) Herculis.
Even small scopes will
resolve many of this cluster’s
stars, and a 6-inch at 100x
shows that M92 is slightly
oval, stretching north to
south. Larger instruments
reveal a large, concentrated
core surrounded by a halo of
hundreds of faint stars.
We’ll end our summer sec-
tion with a trio of globs in
Sagittarius. Start by pointing
your scope 1° northwest of
Lambda (λ) Sagittarii for the
faintest of the three, M28,
which glows at magnitude 6.9.
An 8-inch telescope will let
you resolve a few dozen stars
in its wide halo, which spans
11.2'. Look closely to spot
a bright chain of stars to
the north and a fainter one
to the north-northwest.
Observers have reported a
three-dimensional aspect to
M28 through larger scopes
and magnifications of 250x
or more.
Next up is M22, the third-
brightest globular cluster in
the sky, surpassed only by
Omega Centauri (NGC 5139)and 47 Tucanae (NGC 104),
both of which lie much far-
ther south. This wonder
gleams at magnitude 5.2
and measures 24' across.
Unfortunately, it’s a
southern object, which
means northern
observers must
observe it through
lots of atmosphere.
To find M22, look
2.4° northeast of
Kaus Borealis
(Lambda
Sagittarii).
A 4-inch scope
will resolve 20 or
more stars against a
rich background. Your
first task is to find the
cluster’s edge. An 8-inch or
larger instrument will satu-
rate the field of view with
hundreds of stars. Spend
some time looking for the
many patterns (arrowheads,
chains, geometric shapes)
that are visible.
Our final summertime
globular is M55, which lies
8° east of Ascella (Zeta
Sagittarii). It glows at magni-
tude 6.3 and spans 19'. You’ll
quickly notice that M55
doesn’t have a dense core.
Large scopes with eye-
pieces that provide high pow-
ers (300x and above) will
reveal several hundred faint
stars. And here’s something
fun you can try: Insert an
eyepiece with a tiny field of
view. Through it, M55 looks
more like an open cluster
than a glob.Fall and winter
You might think that after
the summer barrage of globu-
lars, there are none left. That’s
not quite true. The best of
autumn’s three objects is M15
in Pegasus. It glows at mag-
nitude 6.2 and spans 12.3'.
To find it, draw a line from
Theta (θ) to Epsilon Pegasi
and extend it 4°.A 4-inch scope will
resolve dozens of stars
around M15’s bright central
region. Observers specifically
target the cluster’s attractive
chains of stars. Because of
their position, M15 may
appear slightly oval through
a small scope.
If you head south to
Aquarius and look about 5°
north of Beta Aquarii, you’ll
encounter one of my favorite
globulars: M2. This stellar
beehive glows at magnitude
6.6 and measures 12.9' across.
Even a small telescope will
reveal M2’s slightly elliptical
shape, although more north-
erly observers will need
steady air near the southern
horizon. It’s worth the wait.
While you’re in M2’s
neighborhood, head west one
constellation and locate M30
in Capricornus. To find this
magnitude 6.9 glob, look
about 3° east-southeast of
Zeta Capricorni.
M30 has a diameter of 11'.
Through a small scope, you’ll
see lots of resolvable starssurrounding a large, bright
core. To resolve that region,
you’ll need a 12-inch scope
and a magnification of 300x
or more.
Our final object is the lone
entry from the winter sky.
M79 in Lepus glows at mag-
nitude 7.8 and spans 8.7'.
To find it, draw a line from
Alpha through Beta Leporis
and extend it 3.5°.
Small scopes don’t reveal
much detail in M79. However,
a 10-inch instrument shows a
bright, wide core. Use a mag-
nification of 200x or more,
and you’ll resolve scores of
stars at the cluster’s edges.The sky beckons
I hope this list has shown you
that the universe of globular
clusters is a rewarding one
to observe. Indeed, I expect
you’ll add many more details
to the few that I’ve provided
for each of these fascinating
objects. Good luck!Michael E. Bakich is a
contributing editor of Astronomy.DO
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