RAINY CAPE WINTER
NIGHTS remind me of Scorpio. When these conditions finally let
up, the night sky seems particularly black, the stars blazing and the air crisp.
Perhaps its just my senses that are made keener by the anticipation of a clear
From my home town of Stellenbosch, the Scorpions curved
body can be seen rising over a mountain - Stellenbosch Mountain - in the
southeast. From the pincers (beta, delta, pi ) to Antares (alpha Sco) sweeping
upwards through epsilon, mu and zeta, curving down to eta, these stars fit the
mountains silhouette almost exactly. Perhaps there is some Great Cosmic
Significance in the fact that these stars form a celestial crown around the
mountain. Maybe this Alignment indicates that some ancient civilization built
Stellenbosch Mountain as a monument to future generations. Or possibly its
Stellenbosch itself - after all, its over 300 years old - that is significant,
and needs to be landmarked. [Is it mere coincidence that, when seen on a map,
popular pubs in the town are arranged in a figure resembling the constellation
Ara, which rises with the Scorpion? Perhaps authors Hancock and Bouval should be
While you ponder on these and other mysteries, take time out to
examine some of Scorpios gems.
Three open clusters noted by Abbe
Lacaille lie near the Scorpions tail. Near the western extreme of the
tail, where it joins the body, lies two very different clusters, NGC 6124 and
Catalogued by Lacaille in 1755, he saw NGC 6124 as a fairly
big tailless comet which is a pretty good description considering the
optics he used. In modern binoculars, this cluster is a superb half-degree
moderately rich swarm of faint and very faint stars. It appears vague and
nebulous while scanning the area, but is clearly resolved into tiny stars when
closer attention is paid. The stars appear to group together somewhat towards
the northwest of the cluster.
Its worth a look in larger instruments, too.
John Herschel called it loosely scattered, not much compressed in the
middle, fills nearly a field, consists of about 50 or 60 stars. I used a
15.5-inch reflector at 220x to see it as a large, scattered cluster having about
a dozen bright members and many smaller stars. It fits snugly into a 23' field
of view, and invites the eye to connect-the-dots and trace out
asterisms, of which there are many. For example, you can find a tiny Southern
Cross, a Triangulum and a Musca. Hartung commented that it contains
several orange stars as well as numerous pairs, triplets and small groups.
The much different NGC 6231 lies to the east. Halley observed
it from his island observatory on St Helena, and Lacaille, too, recorded it; he
called it a close group of seven or eight close faint stars.
an easy naked eye object, seen as a fuzzy spot where the curve in the Scorpions
tail starts. Binoculars show a stunning, brilliant cluster of bright, white
stars, about 9 across. Burnham fittingly described it as a handful
of glittering diamonds displayed on black velvet. Phil Harrington writes
that one glance will immediately tell you that this object is something
special ... when viewed with an 8-inch telescope at low power, about a quarter
of its stars shine between magnitudes 5 and 13. The remaining suns, all fainter
and unresolved, surround these in a wedge of celestial mist. Larger apertures
and higher magnifications resolves some of the cloudiness into even more stars.
time out to scan the immediate surroundings in binoculars; veteran observer Tom
Lorenzin writes: add the Zeta Sco crowd and this area makes a terrific
binocular field; see the field as the Baby Scorpion which clings to
the back of its mothers tail.
The other end of the tail marks the position of NGC 6475,
better-known as Messier 7. This huge stellar gathering is easily visible with
the naked eye, even on poor nights, or with the interfering Moon, and was known
to the ancients as The Cloudy Ones which Follow the Sting
noted it as a group of 15 to 20 stars in a square and Hartung too
picked up on the linearity evident in this cluster: a remarkable
sight in a large field with its structure of quadrant and straight lines. With
outliers it is more than 40' wide, and very effective for small telescopes.
Just south of the Scorpion lies Ara the Altar, sometimes
identified as the Altar of Noah, an interpretation that is all too fitting with
the wet Cape winters. Although smaller than Scorpio, this grouping also has a
fine collection of deepsky objects. Ill discuss three of the most
splendid, starting with the two nearest Scorpio. NGC 6193 is probably the most
prominent open cluster in Ara, and was first noted by James Dunlop.
cluster is well spread out, and in modest-sized telescopes will reward the
observer with remarkable star chains and stellar knots. Interestingly, the
brightest star in the cluster is a close double star see if you can split
Far more elusive is the nebulosity (NGC 6188) associated with the
cluster; John Herschel wrote: consists of about a dozen stars 10..11
magnitude, and perhaps as many less, with stragglers, which fill field. In its
preceding part is a fine double star ... and yet more preceding is a very large,
faint nebula, in which the preceding part of the cluster is involved.
Although spectacular on long-exposure photos, Ive never seen the
nebulosity through a telescope. If you try to spot it, let me know how you fare.
An altogether easier target lies to the east and a degree
further south. This open cluster, IC 4651, was oddly enough missed by John
Herschel but is readily visible in binoculars. It was catalogued by Solon Bailey
of Harvard College Observatory, who noted it on a photograph of the southern
The cluster is readily found one degree west of Alpha Arae. In
binoculars, it shares the field with a number of brightish paired stars, and
appears as a large (16), faint, irregularly-round patch, mottled, with
three small stars made out. It is a surprisingly large but delicate object, and
quite beautiful. Funnily enough, it reminds me of the Helix nebula!
calls it an irregular gathering of numerous stars fairly uniform in
brightness, about 15' across with stragglers to 20'. The stars are in lines,
curves and chains enclosing dark spaces so that the pattern is open without much
condensation. He recommends at least a 6-inch telescope to view the
I noticed Hartungs dark spaces in the
15.5-inch; at 220x there appears to be a roughly triangular nucleus made up of
about 15 stars; surrounding it are dark star-less patches (one west, one
northeast) which almost isolate the nucleus from the rest of the cluster. These
two voids look somewhat like a pair of lungs!
Ara is also home to NGC 6397, about 4° further south. This
globular cluster forms a 90° triangle with two bright stars (one of which
is pi Arae) as seen in binoculars, which show it as a pretty bright, large,
round stellar gathering, with three small stars seen in the outer reaches. It
grows gradually brighter to the middle, to a broad dense bright disc, 6
across. With averted vision, the cluster expands to delicately cover a 14
circle of sky.
With a telescope, however, the odd nature of the clusters
nuclear region is apparent. Dunlop recorded an interesting description: a
pretty large nebula, extended nearly in the parallel of the equator, brightest
and broadest in the middle; a group of very small stars in the middle give it
the appearance of a nucleus, but they are not connected with the nebula, but are
similar to other small stars in this place which are arranged in groups.
Herschel noted that in the middle is a more compact group of much smaller
stars and on another occasion wrote: very much compressed in the
middle where, however, the stars are very small, while every where else they are
In the Union Observatory Circulars (Nos. 45-76, p 50)
it is called a fine cluster, 15 in diameter, the very centre is
confused and looks nebulous, there are about 150 stars in all.
observer Magda Streicher, of Pietersburg, viewed the cluster with a Meade 8-inch
from the Kruger National Park and called it very large (about 19
arcminutes), bright, round, with a hint of a core. Well-resolved close stars
form arms and trails randomly, with dark patches in-between. See if you
can notice the dark patches she mentions.
On the same Uranometria chart (U 434), but across the border
into Telescopium, lies NGC 6584. This cluster was missed by Dunlop, but picked
up by John Herschel. He noted it as bright, round, gradually brighter
towards the middle, entirely resolved into stars; easily seen . . . easily
resolved with left eye into stars 15th magnitude. [An interesting
personal characteristic appears in Herschels notes. He frequently referred
to observations made with his left eye In his Cape Observations of Nebulae and
Clusters we have for example: 2405, a difficult object but certain after long
attention with the left eye; 3152 all finely resolved into perfectly equal stars
like the finest dust, which are seen with the left eye without effort, but the
right requires to be somewhat strained to discern them; 3690 the right eye does
not resolve or barely makes it resolvable, the left eye resolves it completely
into stars 17...20m. Whether or not he customarily observed with the left eye,
it was certainly superior to the right in resolution and sensitivity.
Lindsay, 1964, IAJ, 6, 286-289]
NGC 6584 is reasonably easy in 11x80s, where
it is easily pinpointed as one corner of a triangle with two 8th mag stars
north. Binoculars show it as a delicate round glow, confirmed with averted
vision as a glow up to 4 across. The cluster does not appear to grow
brighter to the middle.
This quick trip through some of winters highlights must
necessarily come to an end. However, I would like to discuss a group of objects
brought to my attention recently by Gabriel Giust of Buenos Aires, Argentina.
Gabriel is busy working towards his Bennett Certificate, and had been observing
the Bennett objects in the congested region of the Large Magellanic Cloud. The
key to successful observing in the Clouds is to use a good map. Oftentimes one
reads about the complexity of the Virgo galaxy cluster, and how difficult it is
to not get lost. Well, the Virgo cluster should be regarded as a practice run
for the LMC. In the 1920s, R T A Innes wrote that, within the boundaries of the
LMC, are contained, with the utmost profusion, irregular patches of
nebulae, spiral nebulae, nebulous stars, nebulous clusters, loose clusters of
stars, and fine globular clusters. He was planning to resurvey the area
with the 26.5-inch refractor; a start was made in 1926, but a few nights
work indicated that a survey such as contemplated would take several years and
would seriously interfere with the double-star program to which this observatory
The brightest object within the LMC is the well-known
Tarantula Nebula, NGC 2070, one of the southern skies showpieces. NGC 1763 -
Bennett 27 - is part of a busy field of clusters and nebulosity, and was
recorded by Herschel on a number of occasions: very bright, very large,
irregularly extended, irresolvable but thickly dotted with many distinct stars.;
a very bright, very large nebula with stars (the chief of which in the
anterior part of the nebula taken) of a crooked rounded oblong shape. A fine
object.; very bright, very large, irregular oval figure with stars
Gabriel observed it with a 13.1-inch f/4.4 Newtonian: With
37x, I can see a group of three oval nebulae in the field, north-east of a 6th
magnitude star. With 98x - a very beautiful view! The field is very rich in
faint stars between many nebulae. The brightest of these is extended NE-SW, and
has a straight line in its interior. Examining the Uranometria chart, I conclude
this one is NGC 1763.
The chart below, taken from LMC Selected
Areas shows this region and identifies a number of NGC objects. I
recommend this set of charts to any observer who wishes to delve into the
treasures of the LMC; write to M. Morel, 18 Elizabeth Cook Drive, Rankin Park,
NSW, 2287, Australia, for details.
As always, correspondence is welcomed at PO Box 12838,
Stellenbosch, 7613, or via email to firstname.lastname@example.org