Astronomy - USA (2020-06)

M15

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subdivide into varied patterns

that hide the central chain.

Finally, look carefully 0.6°

northwest of Antares for

NGC 6144. At magnitude

9.0, this glob glows only 4

percent as brightly as M4.

Still, it’s easy to spot from

a dark site. NGC 6144 has a

diameter of 9.3'. Through an

8-inch scope, use high powers

to resolve the stars at the clus-

ter’s outer edges.

Now, head north

from Scorpius to find the

Hercules Cluster (M13),

which, at magnitude 5.8, is

second in brightness only to

M5 in the northern half of

the sky. M13 is more than 30°

higher, however, so observers

target it much more often.

This globular also appears

brighter than M5 to most

observers because it’s slightly

smaller, spanning 16.6'. That

makes its surface bright-

ness a bit higher than

M 5’s.

To find M13, look

two-thirds of the

way from Zeta (ζ)

to Eta (η)

Herculis. Through an 8-inch

or larger scope, this glob has

character. Use an eyepiece

that gives a magnification of

200x or more and you’ll see

the Propeller, a Y-shaped

region of three dark lanes

near the core. High powers

also cut the brilliance of

M13’s core, which can mask

some of the details visible at

the edge of the cluster.

Our next two treats lie in

Ophiuchus. M12 lies 7.7° east-

northeast of Yed Posterior

(Epsilon [ε] Ophiuchi) and

glows at magnitude 6.1, which

makes it barely visible to the

naked eye from a dark site.

Through a 4-inch tele-

scope, you’ll see a faint halo

around a tiny core. A 10-inch

scope at high power, however,

gives a deep view, resolving

the cluster into hundreds

of stars. This is when you’ll

notice how evenly distributed

Large scopes

with eyepieces

that provide high

powers (300x

and above) will

reveal several

hundred faint

stars.

M22