By Jane Houston Jones
from Nov 2002. Sky & Telescope Magazine, p. 107.
sights make up the "other" Herschel
catalog. Most are in view this season. Can
you log them all?
WHEN I GAZE AT CANIS MAJOR sparkling on a
cold night I sometimes time-travel back to
1783. I picture Caroline Herschel, age 33,
at her small telescope near Windsor, England.
The Sun has set, her older brother, William
Herschel, is out of town, and she is about
to make a discovery that now bears her name.
Two years earlier William had become famous
by discovering Uranus. On quiet nights when
he was away, Caroline swept the sky with her
small reflector for discoveries of her own,
particularly comets. Caroline did not have
much free time. When William was at the eyepiece
of his 20-foot-long reflector she was always
there with pen and ledger, recording his observations
of faint deep-sky objects. On cold winter nights
the ink sometimes froze in her inkbottle. William
kept his telescope aimed at the meridian; Caroline
noted the elevation of each object he sighted
and the sidereal time, as well as his spoken
comments, and the next day she reduced the
many readings into right ascensions and declinations.
Then she would plan the next night's observing
schedule. Nearly 2,500 of these "Herschel objects" would
form the core, a century later, of the NGC,
the New General Catalogue of Nebulae and Clusters
"Do you know how to find Caroline's Cluster?" a
friend asked me at a club star party on Mount
Tamalpais near San Francisco early this year.
Her coincidental question jolted me out of
my 18th-century reverie. After collecting my
thoughts, I obliged her by aiming my 12.5-inch
f/5.75 reflector in the direction of Caroline's
Cluster, NGC 2360 in Canis Major, the lovely
object that Caroline discovered with her telescope
that night in 1783.
In addition to hunting comets (she eventually
discovered eight), Caroline Herschel cataloged
13 deep-sky objects of her own while not working
for her brother. Four are in Cassiopeia, and
two each are in Andromeda and Canis Major.
Cepheus, Sculptor, Hydra, and Ophiuchus each
hold one "C. Herschel" object. And a mystery
object in Monoceros has never been identified.
Herschel taking notes as her brother William
observes. This engraving by P. Fouché was
meant to illustrate the pair on March 13,
night William discovered Uranus.
Unlike most other Herschel objects, hers
are generally bright and easy. Many amateurs
are familiar with the selected "Herschel 400" list;
the Astronomical League grants its Herschel
Award to observers who log all 400, a worthy
goal for amateurs who have recorded the 110
or so Messier objects (see www.astroleague
Caroline Herschels form a small and interesting
subset of the Herschel 400. Why not plan to
observe them this year? Rather than just ticking
off these objects on a checklist, I hope you
will stop and contemplate them for a while.
Imagine the thrill of discovery Caroline must
have felt on those long-ago nights.
Ten of the objects make good fall targets
for Northern Hemisphere observers. Save two
of them for spring and summer stargazes. And
tackle the remaining mystery object in the
armchair some rainy night.
NGC 7789 in Cassiopeia is a beautiful and
well- known open cluster, a rich swarm with,
however, no stars brighter than 11th magnitude.
Compared to many clusters it's delicate and
lacelike. I observed it several times before
someone told me its modern nickname, the Magnificent
Cluster. I first logged it and the other three
C. Herschels in Cassiopeia on November 2, 1997,
with Strider, my brand-new 12.5-inch Litebox
Dobsonian reflector made by Barry Peckham in
Hawaii. I like to observe clusters with a variety
of eyepieces, and each view from 83x to 200x
was different. The lower power yields more
than 100 stars, with some pretty star chains
and many dark lanes. At 200x there's a small,
dark, starless spot in the middle.
NGC 7789 is easy to find 3° southeast of
Beta Cassiopeiae, the easternmost star of Cassiopeia's
W pattern. Caroline discovered it in the fall
of 1783, and it is cataloged in the William
Herschel list as H VI-30, the 30th object in
his Classification VI: "very compressed and
rich clusters of stars?"
NGC 225 is a loose cluster that looks great
in every telescope. It's a cinch to locate
halfway between Gamma and Kappa Cas. To me
it looks like a triangle of triangles, with
one little trail of stars dividing them. About
30 stars show in my 12.5-inch. Caroline discovered
this object in 1784, and it became the 78th
object in Herschel's Classification VIII: "coarsely
scattered clusters of stars?"
NGC 381 is a fainter and smaller open cluster
located just 1.6° northeast of Gamma Cassiopeiae.
With a wide-field Panoptic eyepiece giving
114x in my 12.5inch, it shows a chain of stars
leading toward the center, sort of like a candied
apple on a stick. Unfortunately, it's not plotted
on Sky Atlas 2000.0; you'll have to mark it
there yourself using the position in the table
on the facing page. It's between two 6th- magnitude
stars 1° apart.
NGC 659, our last open cluster in Cassiopeia,
looks like a patch of Milky Way anchored by
a pretty triangle of stars including 44 Cassiopeiae.
I've never seen more than about two dozen stars
in this cluster through any telescope. It's
northwest of Delta Cassiopeiae, quite near
the brighter clusters M103 and NGC 663. The
three-cluster grouping looks great even in
NGC 7380 in Cepheus is a triangular cluster
embedded in a larger, faint emission nebula,
Sharpless 2-142. I first observed this cluster
from my back deck in San Rafael, California,
on December 26, 1997, using my 12.5-inch reflector
at 1 14x. Without a filter I can barely see
the nebula, but a narrowband 0 III or UHC filter
significantly increases its contrast with the
NGC 253 is a big, dusty, nearly edge-on galaxy
in Sculptor famous from photographs. I've observed
it in every telescope I've owned, and it's
one of my all- time favorites. If it weren't
so far south in such a dim, out-of-the-way
constellation it would be almost as well known
as the Andromeda Galaxy, M31. And it's not
that far south. If you can see Antares or Fomalhaut,
you can see NGC 253.
My most memorable observations of it have
been at Dillingham Airfield on the island of
Oahu with the Hawaiian Astronomical Society.
In 12.5-inch Strider at high power I see dark
dust lanes, mottled lumpiness, and an oval
core. In my larger 17.5-inch f14.5 Litebox
(which I've named Hagrid), it takes on more
substance and greater length. Clumpy starforming
regions brighten dramatically into visible
knots, and foreground stars appear embedded
in the galaxy south of the dust lane. Caroline
discovered this glorious object on September
23, 1783, and it is the first object of Herschel's
Classification V: "very large nebulae?"
Ml10 (NGC 205) is the dimmer, less condensed
of the Andromeda Galaxy's two elliptical companions.
My first observation of M110 was in October
1989 on my back deck with Stardust, my homemade
10-inch f/7.3 reflector. I sketched each new
object I observed, and those early sketches
are amusing to look at now. My sketch looks
like a smudged oval, a little brighter in the
middle. It was my 29th Messier object and my
first Caroline Herschel. She discovered it
and the next object, NGC 891, on the same night,
August 27, 1783. What a night that must have
NGC 891 in Andromeda is a classic edge-on
galaxy with a dust lane down the middle. It
holds a special place in both my heart and
logbook, being one of the first deep-sky objects
I viewed through 12.5-inch Strider. Despite
its fame it is dim the dimmest of the C. Herschel
objects - and has a low surface brightness
to boot. But this elongated spindle of light
looks unusual in any telescope that shows it
at all. You're not likely to detect the central
dust lane, however, in less than a 12-inch.
Cluster," NGC 2360 in Canis Major, is relatively
small and compact. It lies 0.4" east of a 5.5-magnitude
star. The frame is 0.90 wide. Photo from Digitized
NGC 2360 is Caroline's Cluster in Canis Major
and a winter favorite of mine. I love its rich
Milky Way background. This irregular-triangular
cluster displays about 40 to 60 stars, depending
on aperture and magnification. In it are lovely
star chains, star clumps, and inky black spots
with no stars at all. My first observation
of it was on January 17, 1998, through 10-inch
Stardust on my back deck. At 58x it looked
oblong with 20 or so stars. In 12.5-inch Strider
at 83x the number climbs to about 50, and the
cluster looks a little like an arrowhead, with
more stars on its western side. One bright
star, 9th- magnitude SAO 152691, highlights
the cluster's eastern edge.
Caroline's Cluster is easy to find. Starhop
from Sirius to Canis Major's eastern "dog ear," 4th-
magnitude Gamma (y) Canis Majoris. Continue
the same distance farther in the same direction
and you'll have it in your eyepiece. It's only
0.4° east of a 5.5- magnitude star. It is incorporated
in William Herschel's list as H VII-12, the
12th object of his Classification VII: "compressed
clusters of small and large stars?"
NGC 2204 is the other C. Herschel open cluster
in Canis Major; it's less than 2° west of the
dog's front paw, Beta (f3) Canis Majoris. In
my 10-inch it is distinct with a bright orange
star just to its northwest. At l42x I see dozens
of stars and several star chains. Caroline
discovered this cluster too in 1783, and William
numbered it just after NGC 2360, as H VII-13.
"NGC 2349," supposedly in Monoceros, is a
mystery object that Caroline apparently cataloged
incorrectly. It remains a puzzle to this day.
William and Caroline recorded a nebula centered
near 7h 10.8w, -8° 36' (in 2000.0 coordinates).
They noted that it is easily identified by
the "extending branch towards the south- preceding" (southwest).
William's son John Herschel, however, later
called it a "poor straggling cluster" and took
its position as that of a double star some
50 seconds of right ascension (12.4') west
of the object observed by his father and his
aunt. He adopted this position in his General
Catalogue of Nebulae, published in 1864, and
John Dreyer perpetuated this position
in his New General Catalogue, published in
M48 (NGC 2548) in Hydra is the one object
in this list best viewed in late winter or
springtime (for the Northern Hemisphere). The
identification of this fine cluster was lost
for nearly two centuries. Charles Messier discovered
it in 1771, but due to an error in data analysis
he gave the wrong position in his catalog so
it was a "missing Messier" until 1959, when
T. F. Morris at last identified it. Caroline
Herschel discovered it independently in 1783,
and William included it in his catalog.
I've observed M48 in every telescope and
binocular I've ever owned. At 62x in Red Dwarf,
my 6- inch f15 reflector made by Pierre Schwaar,
I can see 40 stars including three yellow giants
and two huge semicircles like eyes on either
side of the central ridge. This ridge or chain
of stars forms a nearly north-south nose. Larger
apertures show more stars, including many pretty
doubles. M48 can be seen with the naked eye
in a very dark sky, south of the head of Hydra.
NGC 6633 is an open cluster in Ophiuchus
as large as the Moon, displaying a W-shaped
string of stars as well as other wispy star
chains. Its brightest stars are elongated northeast-southwest.
In my 12.5-inch at 82x I count more than 100
stars, including many colorful yellow, orange,
and bluish ones. This cluster is naked-eye
visible in a dark sky as a bit of detached
Milky Way halfway between Alpha (a) Ophiuchi
and Delta (6) Aquilae. (Larger, looser IC 4756
is 3° to its eastsoutheast.)
A sweep of the Caroline Herschels would not
be complete without observing the lunar crater
C. Herschel in Mare Imbrium near Sinus Iridum.
Day 10 of the lunar month is just about the
best night to observe Caroline's crater. The
next night the great walled plain named for
Caroline's nephew, John Herschel, becomes visible
north of Mare Frigoris. It's more than 10 times
as large, but that's a story for another time.
JANE HOUSTON JONES, president of the Astronomical
Association of Northern California, also enjoys
observing Abell, Barnard, Berkeley, Czernik,
Dolidze, Hickson, Minkowski, Sharpless, Tombaugh,
and Zwicky objects.
The author preparing
Hagrid, her 17.5-inch Litebox reflector, for
a night of viewing at Lake Sonoma, California,
one of her favorite observing sites.