OBSERVING
Deep-Sky Wonders
58 July 2014 sky & telescopean oval glow with a pair of 12th-magnitude stars off its
northwestern fl ank. The galaxy looks about twice as long
as the distance between these two stars, which yields a
length of 2.6′. At 117× these stars are joined by two more
to their southwest. The foursome makes an L shape that
appears backward in my refractor’s mirror-reversed view.
NGC 6643 grows gently brighter toward the center and
appears half as wide as it is long. The galaxy is quite
pretty through my 10-inch refl ector at 213×. Its inner halo
and broadly brighter, oval core are highly mottled. A dim
star sits between the edge of NGC 6643 and the middle
star in the L’s bac k.
Let’s pop in on Psi (ψ) Draconis, which appears
double even in my 9×50 fi nderscope. Through a small
telescope at low power, the 4.6-magnitude primary star
looks yellow-white to me, whereas its 5.6-magnitude com-
panion shines a slightly deeper shade of yellow. Despite
their wide separation, the stars are thought to form a
mutually orbiting pair. The online Sixth Catalog of Orbits
of Visual Binary Stars (William I. Hartkopf and Brian D.
Mason) lists an orbital period of 3,817 ± 500 years. But
the orbit is coded as indeterminate, which means that the
orbital elements may not be even approximately correct.
The asterism Pothier 3 is 1.1°° west of Psi. Together
they make a lovely duo in the fi eld of my 105-mm refrac-
tor at 28×. Pothier 3 is a somewhat butterfl y-shaped group
of 30 stars fl itting across the sky with a wingspan ofnearly ½°. The group was noted by French amateur Yann
Pothier and later determined to be a chance alignment of
stars rather than a true cluster.
R Draconis is a Mira-type variable star, an unstable
giant star whose outer layers periodically expand and
contract. It reached maximum brightness early this June,
and we can follow the star as it falls to its minimum in
mid-October. Its listed range is magnitude 6.7 to 13.2, but
the extremes can diff er by as much as a full magnitude.
NGC 6140 is an intriguing galaxy 1.8° southwest of
R Draconis. My 105-mm scope at 87× only shows a very
small, diaphanous spot when I use averted vision. At fi rst
glance, it’s nothing to rave about even through my 10-inch
refl ector, but careful study discloses subtle features.
At 68× the galaxy’s low-surface-brightness glow has a
11.5-magnitude star near its northwestern border and
a small, elongated, slightly brighter center. At 115× the
galaxy reveals a short, slender bar running northeast to
southwest, which spans a fainter area elongated east-west,
all enclosed in a much larger, gauzy halo. What details
can you glean from this peculiar galaxy?
I think it’s fi tting to wrap up our sky tour with the
closing words from Lucian Kemble’s paper. “Our charm-
ing Dragon, then, while guarding his jeweled treasure
trove and overlooking the wheeling disk of our Sun and
his family, opens to our gaze his bright gems and the dim
cloud of fuzzy galaxies that surround him.” ✦The spiral galaxy NGC 6140 has an unusually small but
bright central bar and intriguingly asymmetric arms.
North is to the upper right in this image.
JOSEF PÖPSEL / STEFAN BINNEWIES / STEFAN HEUTZ