Sky and Telescope - July 2018 - 54

JULY 2018 OBSERVING
Deep-Sky Wonders by Sue French

The
Season's
Top 10
Globulars
Even small scopes can track
down these striking summer
star balls.

J U LY 2 0 1 8 * S K Y & T E L E S C O P E

sion in the cluster's southwestern side.
M2 is quite lovely at 299×, bright and
richly resolved.
Number nine on our list is Messier
62 in Ophiuchus. The refractor at
37× exposes a fairly small, moderately
bright, hazy ball wearing a faint fringe.
It's about 4′ across and somewhat grainy
at 102×. Even at 164× only a few stars
are visible within the conﬁnes of the
cluster. At 166× the reﬂector uncovers
many faint to very faint stars in the 5′
halo and 1½′ outer core, which grows
denser and brighter toward the center.
The core appears rather ﬂattened on its
northwestern side.
Our eighth-place cluster is Messier
92 in Hercules. In the refractor at 37×,
its large halo is decorated with pinpoint
stars, and the relatively small core
holds an intensely bright center. M92
is generously ﬂecked with stars at 102×.
u Michael Vlasov sketched his impression of
M2 as viewed through a 10-inch f/5 Newtonian
reflector at 240×. M2 is a symmetrical globular
with a bright core. Look for the attendant star
at the cluster's eastern side.
uu At low power, M3 appears as a soft gray
spot on a gray background. Increasing the
magnification pops up several pinpoints of
light. Jeremy Perez sketched M3 on a night of
average seeing as viewed through an 8-inch f/6
Newtonian at 120×.

p M62 is one of the closest globular clusters
to the center of our galaxy. Galactic tidal forces
affect the distribution of M62's stars, displacing
them to the southeast. This gives the northwestern side of the cluster a flattened appearance in the eyepiece.

The halo covers about 7′, and the 2′
core harbors a small, very bright center.
At 164× at least 25 stars freckle M92's
face, the fainter ones winking in and
out of view. Turning to the reﬂector at
187×, this attractive cluster boasts nice
swirls of stars that bring to mind the
arms of a spiral galaxy. The cluster is
well resolved into stars down to its brilliant core, whose center appears vaguely
triangular.
NGC 6541 in Corona Australis
should be seventh, but cresting only
M2
N
M 62: N ASA / ESA / STSCI / S. A NDERSON / J. CH A N A ME

lobular clusters are ancient
systems with tens to hundreds of
thousands of stars packed into a globe.
While open clusters are generally conﬁned to our galaxy's disk, globular clusters inhabit an enormous sphere around
the galactic center. Let's take a look at
this season's top ten globulars, cherrypicked by the following rules. They must
be within the domain of the all-sky
chart at the center of this magazine,
with their ranking determined by visual
magnitude according to the Catalog of
Parameters for Milky Way Globular Clusters, 2010 edition, compiled by globularcluster maven William E. Harris.
Holding 10th place in our countdown, Messier 2 resides in Aquarius.
Through my 130-mm refractor at
37×, M2 is a bright little guy with a
faint halo reaching 4.4′ northeast to a
9.9-magnitude star. At 102× the halo
becomes grainy with one standout star
near the core's eastern side. The view at
164× shows quite a few stars in the halo
and the outer part of the core, but the
inner core is just a mottled glow. In my
10-inch reﬂector at 187×, many stars
adorn the cluster. Its oval core is very
bright and enfolds an intense nucleus.
Dark lanes dwell beyond the core, one
northeast and a less obvious one southsoutheast, and there's a shadowy incur-

Sky and Telescope - July 2018

Table of Contents for the Digital Edition of Sky and Telescope - July 2018