DAN^ CROWSONThe Last
Rites of
Spring
Ignore the call of summer
to explore the spring’s bestgalaxy cluster.
This deep-sky image reveals the complex structure of the spiral galaxy
NGC 4647. Seemingly on the verge of touching the brilliant elliptical galaxy
M60, NGC 4647 shows few signs of interaction with its galactic “neighbor”.48 JUNE 2019 • SKY & TELESCOPE
JUNE 2019 OBSERVING
Celestial Calendar by S. N. Johnson-Roehr
NGC 4647M60I
t’s true that June is the month of
solstice, when summer begins for
the Northern Hemisphere, but I often
spend the month fi nishing up my spring
observing plans. Yes, the temptations of
summer are rising in the east, but the
vernal constellations haven’t yet disap-
peared in the west. And since spring
weather often cuts short my observing
sessions — or eliminates them alto-
gether — I’m willing to postpone sum-
mer to spend a few more hours with
the Virgo Cluster (sometimes called the
Virgo-Coma Cluster).
Just a glance at a star chart covering
the sky between Gamma (γ) Virginis
and Gamma Comae Berenices shows
the potential of this celestial hunting
ground. The Virgo Cluster contains as
many as 2,000 galaxies, of which about
150 fall within range of small scopes.
My 5-inch f/5 refl ector does a solid
job picking out the cluster’s brightest
members (and under very dark skies I
can nab some with the 90-mm refrac-
tor and averted vision), but the 10-inch
f/4.5 refl ector makes the pursuit notice-
ably less strenuous.
The brightest galaxies in the Virgo
Cluster are those included in the
Messier catalog. Most of these can be
found in the stretch between Epsilon (ε)
Virginis and Beta (β) Leonis; a notable
exception is M64, which lies deep in
Coma Berenices. If this is your fi rst diveinto the cluster, the Messiers are a good
place to start.
A few caveats. First, though the chart
on the facing page makes it seem as if
the sky is lousy with galaxies, it takes
a careful star-hop to land one of these
beasts in the eyepiece. Randomly point-
ing your scope toward a populous patch
seems as if it should turn up something,
but keep in mind that your eyepiece
fi eld of view is small compared to the
amount of sky covered in our chart.
Second, magnitude can be a little
misleading when it comes to galax-
ies — surface brightness (brightness per
unit area) can be a better indicator of
visibility. If a galaxy’s light is spread out
over a large area, its surface brightness
is lower. All other things being equal, if
you’re looking for two 10th-magnitude
galaxies, the one with the more favorable
surface brightness (lower number) will
probably be easier to fi nd. It’s not a per-
fect system, but if your atlas lists both
magnitude and surface brightness, use
them to guide your observing choices.
Third, most of these galaxies aren’t
showpieces. While the Virgo Clusteroffers its share of spirals (M90 in Virgo,
M88 and M64 in Coma Berenices) and
lenticulars (M104, south of Gamma
Virginis on the Virgo-Corvus border),
most of what you’ll be chasing are ellip-
ticals, which look like blurry rice puffs
in the eyepiece. But it’s the number of
galaxies gathered near the cluster’s core
that’s important, not the aesthetics.
There are several ways to approach
the Virgo Cluster. Beta Leonis is a sen-
sible starting point for a star-hop to 6
Comae. The edge-on spiral galaxy M98
is about ½° west of this 5th-magnitude
star, and the pair shares a fi eld of view
at low magnifi cations. The face-on
spiral M99 lies less than 1° southeast of
6 Comae. A line drawn from 6 Com to
M99, then extended about 2^11 / 3 ° beyond
the galaxy takes you right to the M84–
M86 galaxy pair. These two ellipticals,
which form the western end of the “gal-
axy asterism” known as Markarian’s
Chain, make ideal jumping-off points
for star-hops to most of the remaining
Messier and not a few NGC galaxies.
Since M60 is my favorite galaxy in
the area, I prefer to start my observing