Sky and Telescope - July 2018 - 60
JULY 2018 OBSERVING
Going Deep by Ken Hewitt-White
Finishing In Lyra
Continuing 4° west-northwestward
took me into southeastern Lyra. There,
in a pretty ﬁeld ½° southeast of a 6thmagnitude orange variable star, is the
globular cluster Messier 56. Although
M56 possesses a total visual magnitude
of 8.3, its leading members are barely
13th magnitude, and those in its popu60
J U LY 2 0 1 8 * S K Y & T E L E S C O P E
lous horizontal branch are about three
magnitudes lower. The modest starball
is loosely concentrated and under 9′ in
diameter. Fortunately, big aperture can
bring a little globular to life.
The view at 84× featured a broad,
mottled mass, its periphery lightly
salted with pinprick stars. A 10.2-magnitude "guardian" star glared 2′
westward. At 228×, I counted perhaps a
dozen 13th-magnitude members on the
cluster's face. Teensy pinpoints glimmered in between the leaders, and a
couple of lumpy "arms" radiated northwestward. At 411×, the arms crystalized into chains of stars; indeed, much
of M56 was resolved. The high power
p SMALL BUT ATTRACTIVE A striking
characteristic of the cluster NGC 6834 is the
straight row of five prominent stars stretched
along its northern portion. The dimensions of
the image are approximately 30′ × 20′.
also yielded a dim companion aside the
10.2-magnitude guardian star.
To ﬁnish off, I visited Lyra's "other"
planetary nebula, NGC 6765. I got
there from M56 by shifting ½° northwest to the earlier-mentioned 6th-magnitude orange variable, then heading
1° westward. My path took me just
north of a superb, 10″ binary. Struve
2483 displays 8.1- and 9.2-magnitude stars together with an unrelated
9.6-magnitude attendant 70″ southwest. Shortly after that attractive set, I
spotted two 10th-magnitude reddishorange stars 8′ apart. They framed a
30″-wide pair of 11th- and 12th-magnitude stars aiming north-northeastward
roughly toward the 12.9-magnitude
planetary, 2′ away.
t TINY CELESTIAL FOOTPRINT The preplanetary nebula M1-92, dubbed Minkowski's
Footprint, is a challenging, high-magnification
target. Can you detect its two lobes as separate components?
NGC 6834: POSS-II / STSCI / CA LTECH / PA LO M A R OBSERVATORY; M1-92: ESA / HUBBLE / N ASA
two, 2.3′ apart). This is a rare preplanetary nebula: an ejected gaseous shell not
yet fully heated to emission. M1-92's
"footprint" results from two shells, or
lobes, one of which is expanding toward
us, therefore looking bigger and brighter
than the opposite lobe.
Ofﬁcially, M1-92 sports dimensions
of 20″ × 4″, though to my eye it was
a terribly tiny blob. Its binary nature
eluded me until I applied 228× and
perceived something star-like on its
southeastern side. At 411×, the lesser
component remained virtually stellar (the 9.7-magnitude star mentioned
above was handy for comparison), but,
happily, the increased magniﬁcation
did create a narrow lane to separate the
"sole" and "heel" of Dr. Minkowski's
intriguing celestial foot.