M80NGC 6144M4t
tlo/ibmkSCORPIUSOPHIUCHUSLIBRAsAntaresSh 225 GraffiasSh 2263°72 ASTRONOMY • SEPTEMBER 2019
OBSERVING BASICS
L a st mont h, we ad m i red S cor piu s f rom a fa r w it h
the unaided eye and binoculars. We now turn
to our telescopes for an even closer look. In
deference to those who live in mid-northern latitudes, we’ll
concentrate on an area of Scorpius that lies above about
–30° declination. The chart above, taken from Astronomy’s
Atlas of the Stars, shows the location of our targets.
We’ll begin with M4, the globular cluster a little
west (right) of Antares. During a small-
telescope survey of Messier catalog objects
I conducted some years ago, I viewed M4
through a 4-inch rich-field ref lector at 74x,
noting that it appeared oval in shape and
not very “globular.” With a 4.5-inch f/8
ref lector at 152x, I perceived some
resolution — not exactly unexpected, as
M4 is one of the nearest of all globulars.
Can you spot a distinctive band of stars
bisecting the cluster, which was first seen
by William Herschel in 1783?
Next, turn your scope to a spot ½°
northwest of Antares. Here, we’ll find the
9th-magnitude globular cluster NGC- It can be seen with low magnification, but a wide
field will bring Antares into view. Use medium to high
power to keep the bright star out of the way.
Antares also leads the way to yet another globular
cluster — entry No. 80 in Messier’s catalog. To find it,
perform a low-power search of the area midway
between Antares and Graffias (Beta [β] Scorpii). In
notes made during my small-scope Messier survey, I
wrote that M80 was “Unresolved. Tends to show high
concentration towards center.”
T h i s pa r t of S cor piu s abou nd s i n double st a rs , so much
so that I featured it in the double-star column I wrote for
Deep Sky Monthly in July 1979. Headlining the group is
Graffias, a pair of magnitude 2.6 and 4.5 stars separated
by 13.7 ". Wit h spec t r a l cla s se s of B 0. 5 a nd B2 , t he y shou ld
appear snow-white. To me, however, the fainter member
seems blue-green. See if you agree.
Up next is Nu (ν) Scorpii, a “double-double” I featured
in this column a few years ago (“Civil War star,” June
2014). Through a common 2.4-inch refractor at a mag-
nification between 30x and 60x, you’ll see two stars of
magnitudes 4.4 and 6.6 that are a spacious 41.3" apart.
Switch to 150x with a 4-inch scope under ideal seeing
conditions (or a 6-inch or larger if there’s a hint of atmo-
spheric turbulence), and each of these stars is again
doubled. The brighter has a 5.3-magnitude partner situ-
ated 1.3" to its north, while the fainter is attended by a
7.2-magnitude star currently 2.4" to its northeast.
A much easier double-double is Sh 225 and Sh 226
(“Sh” for the British astronomers James South and John
Herschel, who cataloged these pairs in 1824). They
appear as a tight pair of stars 1° immediately west (right)
of Psi (ψ) Ophiuchi. Sh 225 consists of magnitude 7.4 and
8.1 stars separated by 46.6", while Sh 226 is a closer (12.5")
magnitude 7.6 and 8.3 duo.
Next, we turn our scopes to Sigma (σ) Scorpii (magni-
tudes 2.9 and 8.4, separation 20.3"). Despite how far apart
they are, the magnitude difference could make the second-
ary elusive in small scopes, so use averted vision. Because
the companion is west of the main star, it should lead the
way as they drift across your field of view.
If you’re up for a demanding visual
challenge, see if you can spot the 5th-
magnitude companion to Antares, just 3.2"
f rom t he ma i n st a r a nd more t ha n 6 0 t i me s
fainter. To see it, you will need: a 6-inch or
larger scope; as high a magnification as
possible (300x isn’t too much); and, of
course, optimum seeing conditions. As was
the case with Sigma Scorpii, the lesser star
is west of the primary and will precede it as
the pair drif ts across your f ield of view.
This concludes our Observing Basics
look at Scorpius. If you want to dive deeper
into the Scorpion, check out Phil
Harrington’s article “The life and death of stars in
Scorpius” in the May 2019 issue of Astronomy.
Questions, comments, or suggestions? Email me
[email protected]. Next month: We celebrate
International Observe the Moon Night. Clear skies!Let’s complete our tour by zooming in on the Scorpion’s gems.
Tele sc opic targets
in Scorpius
Although the Scorpion
holds many targets
you can explore
with little to no
magnification, a
telescope reveals the
constellation is packed
with double stars and
globular clusters
worthy of a closer look.
ASTRONOMY: ROEN KELLYIf you’re up for
a demanding
visual challenge,
see if you can
spot the
5th-magnitude
companion
to Antares.
BY GLENN CHAPLE
Glenn has been an
avid observer since
a friend showed
him Saturn through
a small backyard
scope in 1963.BROWSE THE “OBSERVING BASICS” ARCHIVE
AT http://www.Astronomy.com/Chaple