Click on a
constellation:
Andromeda NGC-752 Aquila
NGC-6709 Auriga
M-36 M-37 M-38 NGC-1857 NGC-1907 Camelopardalis
Kemble NGC-1502 Cancer
M-44 M-67 Canis
Major M-41 NGC-2360 NGC-2362 Carina
NGC-2516
NGC-3293
NGC-3532
Cassiopeia
M-52 M-103 NGC-103 NGC-663 NGC-457 NGC-7789 Cepheus
NGC-6939
NGC-7419
NGC-7510
ComaBerenices
Melotte 111
Crux
Jewel Box
Cygnus
M-29 NGC-6910 Gemini
M-35 NGC-2158 NGC-2266 Hydra
M-48 Lyra
NGC-6791
Monoceros
M-50 NGC-2244 NGC-2301 Orion
Trapezium
NGC-1981
NGC-2169
Perseus
M-34 Mel-20 NGC-869/884 NGC-1245 Puppis
M-46 M-47 M-93 NGC-2438 NGC-2451 NGC-2477 Sagittarius
M-18 M-21 M-23 M-25 NGC-6530 Scorpius
M-6 M-7 NGC-6231 Scutum
M-11 M-26 Serpens
M-16 Taurus
Hyades Pleiades Ursa
Major Trivia Vulpecula
Coat Hanger
NGC-6802
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Stars show their true colors,
both to the naked eye and in telescopes. Open clusters can be
dazzling displays of vast numbers of colorful jewels. Even those
without color are beautiful, as their spangled brilliance gives an
impression of diamonds on black velvet. If viewed with the right
optics and from a dark location, and with a little patience and
dark adaptation, you may soon be rewarded with a mesmerizing
"space walk"
experience. |
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NGC 752 is visible in small and medium telescopes.
In a 6-inch Newtonian the 50-plus population fills the field of
view at 48 power. This cluster is estimated to be about 1.2
billion years old, or roughly one-fourth the age of our Solar
System. 6-inch
Newtonian |
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NGC
6709 We
include this cluster mostly because it was on the menu of a GOTO
telescope. After keying it in and taking a look, we decided to
make some drawings. This is the result - actually our first
rendering. There is very little written about this cluster, and
most of the available information is either very brief or
contradictory. It is barely mentioned in Burnham's
Handbook. However we do know that this object is best viewed
with larger apertures (8-inches or more). At a distance of 2,500
light years, it contains about 40 stars.
13-inch
Dob |
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Auriga is host to
three dominant open clusters in the Messier catalog. M-36
is one of them. Although M-37 gets most of the attention,
this cluster makes a striking image on a dark and still night.
There are subdued colors here, but one particular sun near the
center looks like a carbon star. 10-inch
SCT |
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M-37 has long
been a favorite of ours. It can tease the imagination. Geometric
figures, animal shapes, clown faces. Look again, and they're gone.
A story book fantasy in the eyepiece. Not much color, but a few
orange suns. 7-inch
Mak-Newt. |
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M-38 is is
about 220 million years old. The brightest member is a 7.9
magnitude yellow giant of spectral type G0, with a luminosity of
900 suns. By most accounts, this cluster’s brightest stars form a
pattern resembling the Greek letter Pi. However, at moderate power
we see a distorted cross, with a central bright star surrounded by
an open stellar circle. NGC-1907 is one moon diameter to
the southwest. 5-inch
refractor |
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NGC 1857 is a
relatively neglected and unstudied object. It consists mainly of
blue main sequence stars, but there are about a dozen red giants
in the central field. Its age is about 180 million years. The
brightest stars are much closer, and probably don't belong to its
own population. They might belong to the very loose cluster
Czernik 20, which is situated north, but extends into the field of
view. A colorful subject for astrophotography.
10-inch
SCT |
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NGC 1907 is
parked in the same cosmic garage as M-38. In fact, you can
get to this cluster by star-hopping from M-38 (only 30 arc minutes
away to the northeast). The two are joined by a faint ring of
stars between them. There is a trace of nebulosity here, but it's
so fleeting we were somewhat reluctant to include it. A difficult
cluster to resolve, but a striking image.
7-inch
refractor |
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Kemble's Cascade
& NGC 1502 Okay, everybody who knew about this one raise your hand.
Yeah, right! Talk about obscurity! The only reason we found it is
because it was listed in a GOTO file, and we got curious. Let’s
face it, when the word “Asterism” shows up on the LED
display, most observers skip over it. After all, how interesting
can asterisms be? Kemble’s Cascade is an asterism.
Nothing really spectacular by itself. Just a long train out in the
middle of nowhere. But it makes an interesting stop - right at
NGC 1502, where the [yellow-yellow] double star
Struve-485 resides. Together, the entire assembly
bears a strong resemblance to a 4-iron. Of course if William
Herschel had included a description of both in his New General
Catalog, and had combined them as one object, it may have enjoyed
far more notoriety in the past 200 years than merely being
mentioned as a small cluster and a nearby
“asterism”. 13-inch
Dob |
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Cancer is a faint
constellation. All of its named stars are dimmer than the Messier
objects within it. M-44 is a bright 3rd magnitude cluster,
which covers over a full degree of sky. It is known as the
"Beehive Cluster", or Praesepe ("The
Manger"). There are about 200 stars here, all about 400
million years old. It makes its best impression at low power, and
in binoculars. 101mm
refractor |
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Although M-44 appears
brighter and gets more attention, M-67 is no slouch when it
comes to putting on a show. It is especially pleasing in small and
medium telescopes. Besides being twice the actual size of M-44,
and five times farther away, it is one of the oldest open clusters
in the galaxy, at between 4 and 5 billion years, or roughly the
same age as the Solar System. It contains approximately 300 stars.
Stephen O'Meara calls this cluster the "King Cobra", noting
its overall S-shape as reminiscent of a snake. Many of its members
have evolved into red and orange giants.
6-inch
refractor |
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M-41 was
independently discovered by Flamsteed, Le Gentil,
and Messier, but was observed as early as 325 BC by
Aristotle. It contains about 100 stars, and is visible to
the naked eye. It can be a spectacular 3-dimensional experience in
large binoculars, and is a stunning sight in any size telescope.
As is the case with almost all open clusters, there is a red star
near the center of the group – a 7th magnitude K3
giant. 5-inch
refractor |
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Caroline's
Cluster It
is aptly named. We hold a special place of high regard for
Caroline Herschel. Her accomplishments, contributions, and
unwavering devotion to science were achievements of profound
inspiration. She discovered this cluster while finding comets to
add to William's catalog. NGC 2360's field of view includes
a 5th magnitude field star, and a curious orange/yellow foreground
star which seems to only show up in larger apertures. This
neglected cluster is a mass of knots, strings, chains, and loops.
We believe we've noticed dark nebulae at three locations near the
center. We haven't been able to locate any good photos to bear
this out. 75 to 100 stars. 10-inch
SCT |
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NGC 2362 is
approximately 25 million years old, and consists of about 60
stars. The brightest star is Tau Canis Majoris, a
naked-eye star of spectral type O8 - extremely hot and very
bright. Tau is a 4th magnitude supergiant, and one of the most
luminous known (fifty thousand times brighter than the sun). It is
a triple star, and under high power the bright primary can be
easily separated from its two bluish companions. This cluster
presents a really nice image in any telescope. The beehive of
inhabitants around Tau can look nebulous at low power. But slip in
a Barlow, and they pop into resolution. Large Alvan Clark
refractor |
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NGC 2516 is
often referred to as the "False Cross", and has been named the
"Southern Jewelbox" because it contains so many
colorful stars. This cluster covers over a full degree of sky, and
is best viewed at very low power or with binoculars. A very nice
image with a widefield eyepiece. There are three binaries here - h
4027 and 4031, and I-1104. All three have eighth magnitude
primaries and eighth to ninth magnitude companions.
101mm
refractor |
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NGC
3293 This
is one of the showiest open clusters in the southern sky. It was
sketched by Art Krohl from a location in the Florida Keys. Visible
only from southern latitudes, NGC-3293 is abundant with hot blue
stars which are only about 6 million years old - hardly a tick of
the cosmic clock. Here are two views from different telescopes, a
medium refractor, and a large Dobsonian. There are a few red
giants in the population. 5-inch
refractor 20-inch
Dob |
|
NGC 3532 is a
bright eliptical cluster of about 150 stars. It covers an area of
sky that's twice the size of the full moon. It is visible to the
unaided eye and is a thrilling sight in binoculars. Various chains
and loops are visible in small telescopes, as well as a few bright
orange stars. Drawn by Art Krohl in the Florida Keys, this cluster
offers a high degree of visual impact. 101mm
refractor |
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M-52 is
located about 6 degrees northwest of Beta Cas. At medium power,
the overall shape of a scorpion can be detected, the tail of which
arcs toward a bright field star to the north. In terms of density,
M-52 ranks third in the Messier catalog. There are about 200 stars
here. 5-inch
refractor |
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M-103 is a
great binocular subject, but it can be difficult to find with a
telescope, especially in urban areas. There are a few dozen
members, one of which is a red-orange supergiant. It's rendered
here after long sessions of cross-eyed delirium at the
eyepiece. 10-inch
SCT |
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NGC
103 Matching NGC and Messier numbers in the same
Constellation? We include this cluster here for reasons other than
coincidence. For even on nights of the highest purity the
attendant nebulosity is a challenge. Yet on other nights it can
literally jump out at you. There are over 140 stars here, and the
visible population increases with aperture size. An interesting
subject, in a constellation that's full of open
clusters. 11-inch
SCT |
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NGC 457 is
called the "Owl Cluster" and the "ET
Cluster". Although it's the brightest cluster in
Cassiopeia, we usually have difficulty identifying either of those
figures. If we stretch the point we might be able to visualize
them, but averted vision is usually required. We've seen a
likeness in photographs, (sort of) but rarely in the eyepiece. Our
image was rendered over time, with many sessions. We enjoy it for
what we see, even when it's not an owl. 6-inch
Newtonian |
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NGC 663 is a
great binocular subject, and easy pickings in small telescopes. In
fact, this view is rendered from the eyepiece of an 85mm
refractor. Not much color, but bright, and pleasing to the senses.
A lot easier to grab than M-103, and much easier to draw!
There are obvious dark lanes which help give this cluster a
distinct but elusive shape. At least two of us see the outline of
a cat. 85mm
refractor. |
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Discovered by
Caroline Herschel, NGC 7789 is about 1˝ billion years old.
It's a very rich and compact cluster with over 600 members. In a
4-inch aperture it resolves into about 50 stars. It is extremely
dense, and in widefield astrophotos it appears almost globular,
and quite discernible against the galactic carpet. There are quite
a few orange giants here. 7-inch
Mak-Newt |
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Although NGC 6939
is an eye-popper in large apertures, it's really boring in
small and medium telescopes. Virtually every amateur who's looked
at this cluster through a medium-sized tube is certain to believe
there's absolutely nothing to see. And why shouldn't they? There's
very little said or written about this cluster. But if you should
chance upon it while at the controls of a big light bucket, you'll
be amazed at what you see - and at what you think you see.
It's all but impossible to get any brightness out of this object
(perhaps due to several magnitudes of extinction), but there's
plenty of strange shapes, arms, monsters and tentacles to keep
your imagination busy. Every now and then we see a grinning
lecherous rat. Spiral galaxy NGC 6946 is very close,
and can be seen in the same field of view at low
power. 20-inch
Dob |
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NGC
7419 We
literally stumbled upon this one. We had no information on it,
except for the display-coordinates on our GoTo
& Tracking Systems'
computer screen. We found it at RA:
22-54-18; DEC: +60-50-00. Some searching
turned it up in Burnham's and in the Night Sky Observer's Guide.
It's a fairly concentrated group, with 20 to 40 members. The three
brightest stars appear to be magnitude 10 & 11. This image was
rendered at 166 power. Some nice color - at least three
yellow-orange suns. 5-inch
refractor |
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NGC 7510 is a
distant but bright cluster, visible at low power as a hazy smudge.
At moderate power, there’s a hint of surrounding nebulosity (the
"edges" of a large nebula - Sharpless 2-157). At high power,
approximately two dozen of this cluster's 60 or so stars can be
resolved, and the nebulosity is replaced by background
condensation (slip in an O-III filter, and parts of Sh2-157 will
loom into view). The cluster can be almost entirely resolved in a
24-inch Dob. In long-exposure astrophotos, it maintains its
definition even against the chaotic carpet of the starry
background. This is one of those little-known objects that can
make you wonder why it isn’t more popular.
20-inch
Dob |
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Melotte
111 Coma
Berenices is largely comprised of a single open cluster – Mel 111.
The cluster's triangular shape lends visual continuity to the name
of the constellation – which means “Berenice’s hair”. Mel 111
covers almost 4 degrees of sky, and cannot be viewed well in most
telescopes, but is a fine subject in finderscopes or binoculars,
and through a very low-power eyepiece (a TeleVue Pronto or TV-85
is ideal for a cluster of this size). 85mm
refractor
But if you do use high power,
you can look right through Mel 111, and out into intergalactic
space. There you will find two nice galaxies - NGC 4494,
(mag 9.7) and the superb and famous edge-on spiral, NGC
4565 (mag 9.4). They are part of the Coma-Virgo cluster
region. (See them in our Galaxy
Drawings). |
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The Jewel Box
Cluster (NGC 4755). One of the truly colorful views of the night sky.
The Jewel Box is estimated to be only 7 million years old. The
four brightest stars are supergiants. A very bright and showy
cluster, and a great astrophotography subject.
11-inch
SCT |
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M-29 Understated elegance. Like a clutch of pearls, M-29 is
easy pickings for small and medium optics. This cluster would
shine much brighter if not for an adjacent abundance of
interstellar dust a thousand times thicker than normal. Along with
M-37 and a few others, it tops our list of favorites. Do you see a
similarity to the Pleiades? 6-inch
refractor |
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NGC 6910 is
visible in small telescopes. It's called the "Y" cluster
(for obvious reasons). It's also called the "Rocking
Horse Cluster" for reasons that are only apparent if you
see it at a certain "tilt". The view gets more interesting with
dark adaptation, as the background begins to fill
in. 101mm
refractor |
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M-35 contains
up to 300 stars, and is an excellent object for any small
telescope. Particularly nice in a 6 or 8-inch at low power.
Although the center areas seems to be vacant, with very little
"fill-in" condensation to pack the voids of blackness, this
cluster is nonetheless a beautiful example of what's available to
smaller and more modest instruments. Robert Burnham Jr. wrote in
his Celestial Handbook: "... curving rows of glittering lamps
on a chain... fainter stars form a sparkling background with an
orange star near the center." 6-inch
Newtonian |
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NGC 2158 often
shows up in the same field of view as the more famous M-35 (˝
degree southwest). But at a distance of almost 17,000 light years,
it of course appears much dimmer and smaller, and can actually
look like a comet. At high power, and with larger apertures, it
can be fairly well resolved. 20-inch
Dob |
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NGC 2266 is
10,000 light years distant, and about a billion years old. Many of
its stars have already evolved into red giants. Again, this image
was rendered under high power, and with the aid of a very large
telescope. 20-inch
Dob |
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M-48 Messier discovered this cluster in 1771, and then promptly
lost it. Apparently, he'd recorded its coordinates with a 5-degree
error in declination. Caroline Herschel independently rediscovered
it in 1783. Her brother William included it in his New General
Catalog three years later (NGC-2548). There are about 80 stars
here, and most are resolvable in small telescopes. To many
observers the cluster generally looks like an arrowhead. It can
also look like one of those ubiquitous longhorn cattle-skulls that
litter the desert landscape in old western movies. A nice subject
in any aperture. 8-inch
Newtonian |
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Wow! The mother of
all open clusters! NGC 6791 is the oldest open cluster
known, at over 7 billion years. Its exact age is not yet fully
agreed upon. As open clusters go, it is one of the most massive;
it includes at least 17 variables; and its population contains a
high level of metallicity. Naturally, the bigger the aperture the
more it is resolved. There are some orange giants in the field.
Extremely interesting, and quite stunning.
20-inch
Dob |
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By most accounts,
M-50 is unremarkable, and not too thrilling from urban
locations. It does quite well however, against a dark sky. There
are some red and orange giants around, but most of them aren't
part of the group. This is a great subject for CCD work! The
cluster is shaped like a house or a heart. You
decide. 10-inch
SCT |
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NGC 2244 is a
cluster of about 40 stars, situated in the center of its
birthplace - the Rosette Nebula. This nebula is a
super-massive cloud of gas and dust, (130 light years in diameter)
that contains the equivalent mass of about 10,000 Suns. At a
distance of 5,500 light years, it still accounts for a full degree
of sky, which is about twice the apparent size of the full moon.
Because of its low surface brightness, it can be difficult to see
from urban locations. However, it presents itself quite well at a
dark site, rendering a breathtaking image that can rival almost
anything else in the Winter sky. UHC, Ultrablock, and OIII filters
can enhance the nebulosity to a great degree. Some observers even
stack them together. This is how it can look from a very dark site
without a filter. 8-inch
Newtonian
One of the brighter stars is
12 Monocerotis, a yellow super giant about 5,000 light
years closer to us, and is therefore not part of the
population. (For a better look at the Rosette see our Nebula
Drawings). |
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NGC 2301 is an
esoteric favorite among veteran observers. It's easily located in
finder scopes, and best viewed at low power with a widefield
eyepiece. This cluster spans about 16 arc minutes, and delivers a
really nice image in binoculars and small telescopes. About 60 to
70 stars. Many descriptions account for a bright orange star near
the center. At really dark sites, the background condenses into a
stellar carpet. 101mm
refractor |
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Theta1 (q1) Orionis, [The
Trapezium] is possibly the most studied of all multiple
star systems, and arguably the most visually provocative. It is
certainly situated in the right spot for all the attention - right
in the core of the Great Orion Nebula. This small
group is actually part of a massive cluster consisting of about a
thousand stars. Most are hidden from view by a vast amount of
nebulosity and dust. When photographed in infrared, they present a
sobering vista. These are some of the youngest stars in our
galactic vicinity, at an age of only a million years or so. Our
Solar System is 4,000 times older. 6-inch
refractor (For a better look at M-42 see our Nebula
Drawings). |
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NGC 1981 is
the fuzzy patch that makes the handle of Orion's sword. It's
composed of about a dozen icy-blue stars that are very young and
very hot. It can be seen well in binoculars and finderscopes, and
at darker sites it is visible to the naked eye. This neglected
cluster makes a startling image in almost any
telescope. 5-inch
refractor |
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Yep, it really looks
like this! NGC 2169 is called the “37” cluster or the “XY”
cluster. Some observers see the outline of a shopping cart. As
you’d expect, Orion is loaded with double stars and clusters. This
particular cluster is the home of Struve 848, a multiple
star system containing 5 bright suns which are easily
resolved. 5-inch
refractor |
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M-34 is simple
but interesting. It appears to be comprised almost exclusively of
double stars. Though that's not the case, the central star is
h1123, a double from which all the other members seem to be
emanating. Not much color, but nice in small scopes, or at low
power. 85mm
refractor |
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Melotte 20 is
referred to as the Alpha Persei Association, because
the stars in this group were once thought to be unrelated.
However, this is in fact a large cluster, with a span of over 2˝
degrees. Alpha Persei (visible to the naked eye) is the
brightest star in the group, and usually displays a wheat-color in
telescopes. This cluster resides in the same neighborhood as the
California Nebula. Best viewed with binoculars or a
richfield scope. About 120 stars. 101mm
refractor |
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NGC 869 & 884
- double cluster Wow! These two clusters are a thrilling sight in a
rich-field format. To the naked eye, they appear as fuzzy patches
between Perseus and Cassiopeia. In a 5-inch or larger aperture,
with a wide-field eyepiece, they can offer the observer a
colorful, 3D “spacewalk”. Included in the field of view at no
extra charge are several stars of brilliant color (lots of
red-orange). As your dark-adaptation increases, and as the Milky
Way condenses into a spangled background, the image becomes more
and more spectacular. Very high on our goosebump list. This image
was rendered over time, with a borrowed 22mm Nagler, and a Meade
Ultrawide. 101mm
refractor |
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NGC 1245 is
accessible with small and medium telescopes, and is one of the
best astrophoto subjects we know of. There are several bright
orange stars, and a brilliant red one. The two brightest stars to
the east (left) are foreground field stars. One is a rich blue
color. 8-inch
Newtonian |
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M-46 can be a
momentary show-stopper. There's a planetary nebula (NGC 2438)
conveniently perched in the field of view. Although it isn't a
member of the cluster's population, the combination presents one
of the most interesting views in the night sky.
10inch
SCT
The planetary is visible in
8-inch scopes from dark sites, but the central star (at 17th
magnitude) will only show itself in much larger apertures. The
total population of M-46 is about 190 stars. A colorful subject
for astrophotography, as the planetary glows a brilliant red. 10-inch
SCT |
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M-47 contains
a few 5th & 6th magnitude stars which are resolvable with the
naked eye at darker sites. There are two or three orange stars in
the field. We're not certain if they're part of the population.
About 120 stars. 8-inch
Newtonian |
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M-93 makes a
striking image. Like a handful of bright gems against a background
of slightly dimmer ones. The combination can be mesmerizing. If
you have the right optics, you're in for a "spacewalk"
experience. 8-inch
Newtonian |
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NGC 2451
and 2477 - double cluster Wow! These two clusters are located
just 1˝ degrees apart. With 2451 dominating the field of view,
2477 can take on the appearance of a loose globular (it's the
fainter, more distant cluster to the lower left). On its own, at
higher power, 2477 becomes a breathtaking field of sparkles and
light - there are over 300 stars here. This image was rendered
with a richfield refractor and a low-power widefield eyepiece. The
two make a nice image in binoculars and
finderscopes. 101mm
refractor
NGC 2477:
This is one of the most
spectacular open clusters in the southern winter sky. Situated
about 2˝ degrees northwest of Zeta Puppis, the cluster spans the
size of the full moon and contains stars ranging from 10th to 14th
magnitude. It lies some 4,000 light years distant and has been
estimated to be nearly 1.3 billion years old. In binoculars or
under low telescopic power it's a beautiful fuzzy patch - like a
tattered cotton ball. Resolution increases dramatically with
aperture size. At higher power it assumes an odd shape, like a
falling clutch of jewels, with lighter strands trailing in its
sparkling wake. Shapley, in his book Star Clusters.calls it "...either the richest of
galactic clusters, or the loosest of globulars."
20-inch
Dob |
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M-18 lives in
a tough neighborhood. It's situated between the Omega Nebula and
the carpet of stars at M-24. Maybe that's why it gets no respect.
But take a look. What's not to like? There are blue, yellow and
orange stars here. A good subject for astrophotography. About 25
to 30 stars. 8-inch
Newtonian |
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M-21 In larger apertures, a dozen or so stars appear to form an
almost perfect circle, lending a diamond ring appearance to this
cluster. Trumpler classified M21 as I-3-p (poor, or under 50
stars). In 1953 it was shown to contain 57 stars, which
reclassifies it as I-3-r (richly populated with a strong
concentration at its center). The brightest stars here are giants
of spectral type B0 (very hot!). This implies that this cluster is
very young (about 4˝ million years). It is part of the
Sagittarius OB1 stellar association. 8-inch
Newtonian |
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M-23 can be a
magnificent sight in instruments of all apertures including
binoculars. It contains at least 150 stars, most of which are
between 10th and 13th magnitude. At low power, it can be found
hiding in a notch in the frenzied carpet of the Milky Way. All the
way up to medium power a bright 6.5 mag foreground star can remain
in the field of view. Prolonged observing sessions and dark
adaptation have brought about the perception of dragonflies,
spiders, and O'Meara's bats. 7-inch
Mak-Newt |
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Although easy
pickings in even the smallest telescopes, M-25 has only
achieved an IC number. John Herschel didn't include it in his
General Catalog (although it had been observed by de Cheseaux and
Messier prior to 1764). It was finally added to the second Index
Catalog in 1908. Two class M and a pair of class G giants reside
in the field of view. The G’s appear to belong to the population,
where the M’s are merely field stars. M-25 contains the Cepheid
variable U Sagittarii, which places the cluster's age at
about 90 million years. There are between 80 and 100 stars here.
In a 10-inch aperture, with a borrowed 35mm Panoptic, the cluster
is completely resolved and fills the entire field of view. M-25
appears to be split in half by a dark nebula.
10-inch
SCT |
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NGC
6530 An
open cluster in M-8 (the Lagoon Nebula). What could be
better? The surrounding nebulosity is obtainable with a UHC or
Ultrablock filter. On really clear nights there is a considerable
amount. There are several dozen hot young stars
here. 11-inch SCT
(For a better look at M-8 see
our Nebula
Drawings). |
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The brilliant expanse
of sky that represents the glow of the galactic hub is where
you'll find the two stars that make up the scorpion's stinger. The
"Butterfly Cluster" (M-6) lies in this area, and is
visible to the naked eye. It's comprised of about 325 stars, one
of which is BM Scorpii, a semi-regular orange variable that
shines at magnitude 5.5 at maximum. M-7 is also in this
area. 8-inch
Newtonian |
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Covering a full
degree of sky, M-7 was known by Ptolemy in 130 AD. At 3rd
magnitude, it is visible unaided at southerly dark locations. It
never really got the credit or credence it deserves though (even
from Messier). As a result, modern amateurs tend to ignore it. But
this cluster is really a sight to behold in moderate apertures.
M-7 is approximately 200 million years old, and some of its more
massive suns are displaying the geriatric signs of evolution –
some golden-orange giants dot the cluster's landscape, and they
make for a very nice image against the Milky Way background. About
80 stars. 101mm
refractor |
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There's no color here
to speak of, but NGC 6231 owns a solid place among our
favorites. It lies where the scorpion's body joins the tail. It is
a cluster of intense light that rivals even the Pleiades in
brightness. In fact, if it were as close, it would outshine the
Pleiades by several magnitudes (its brighter stars each comparable
to Sirius). This is pure beauty in the eyepiece. In the words of
Robert Burnham Jr., "Like a handful of diamonds on black
velvet". 7-inch
Mak-Newt |
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M-11 is also
called the "Wild Duck Cluster" since Admiral Smyth
noted the presence of a well-defined V-shape, like a flock of wild
ducks. Hmmm. Sorry, but we've always had trouble with that.
Stephen James O'Meara thinks it looks more like a tick. At any
rate, this is about as good as it gets as far as open clusters are
concerned. There are estimates of up to 3,000 stars here, with as
many as 600 at brighter than 14th magnitude. The surroundings are
first rate. When you get over the impact of M-11, take a tour
around the neighborhood with a widefield
eyepiece! 11-inch
SCT |
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In medium apertures
M-26 is easy to miss. It's a faint glow in a 5-inch
refractor at low power. But if you pump up the volume, you'll see
a nice image of a fairly rich cluster. There appears to be an area
of total and complete extinction (roughly in the shape of a
figure-8) in the center of this cluster. Since absolutely nothing
shows through it from the Milky Way background, we assume it to be
a dark nebula. 7-inch Mak
Newt |
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The star cluster
M16 was actually discovered by de Cheseaux in 1745. Almost
20 years later, Messier noticed that these stars were surrounded
by “a faint glow”. Modern astronomy refers to that glow as the
“Eagle Nebula”. The two objects however, though
considered synonymous, are somewhat estranged in their catalogs.
William & John Herschel omitted the nebula from their
directory because they never saw it. Thus, the star cluster alone
is given the listing NGC-6611, while the famous
nebula that gave them birth is recognized only as
IC-4703. Referring to both as “Messier number
16”, although arcane, is entirely logical.
Large
Alvan Clark refractor
This cluster was hatched five
and a half million years ago, from a gaseous dusty amalgam, almost
7,000 light years distant. The high-energy radiation of the
group’s massive hot, young stars (spectral type O6) causes the
nebula to glow under their influence. This is one of the most
photographed and studied regions in our known
universe. (For
a better look at the Eagle Nebula see our Nebula
Drawings). |
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The Hyades –
the Face of The Bull. The bright orange Alpha-star of Taurus
rides proudly along in the field of view with the Hyades cluster.
The star appears to follow the Pleiades cluster across the
sky. In fact, its Arabic name (Aldebaran) means "the Follower".
Since ancient times, it’s been perceived as the Eye of
The Bull. Although it’s not part of the population, it is
prominently featured in the glittering expanse of the Hyades, (it
lies in the foreground at about one third the cluster’s distance).
Aldebaran is an orange giant in the advanced stages of its
evolution. Recent observations of a “wobble” suggest that it
possesses either a massive planet (11 times the size of Jupiter)
or a lifeless sub-stellar companion (a brown dwarf). A great
subject in binoculars and finderscopes. TeleVue
Pronto
The Hyades cluster is far too
extensive for most telescopes to gather in one view. An exception
is the TeleVue Pronto equipped with a 55mm Plossl. This
strange-looking combination yields a field of view that spans 5˝
degrees of sky, (or 11 moon diameters) and yields extremely
high-contrast images. At a dark site it can render a breathtaking
"spacewalk"
experience. |
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M-45 – [the
Pleiades – Subaru – the Seven
Sisters]. Perhaps the most renowned open cluster in the northern
sky. Certainly the brightest! And big! The main group (visible to
the naked eye) is shaped somewhat like a “mini-dipper”. It’s
almost impossible to get it all in one field of view. The widest
views we’ve seen managed is with a finderscope, or with a
TeleVue-85 or 101 and a Nagler the size of a hand grenade. The
characteristic brightness level of this object is almost
overwhelming. When viewing it, be sure to give your dark
adaptation a goodbye kiss. The nebulosity that surrounds these
stars is fleeting in the eyepiece, even under ideal conditions.
Yet all but the poorest astrophotos of this cluster are stunning
displays of a sapphire arrogance. We show it here as it looks at a
dark site, with widefield optics. 85mm
refractor |
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You decide:
What does it look like? We’ve long had the notion that the Pleiades cluster
closely resembles another object of equally exalted status. As an
experiment, we converted a picture of M-45 to black and
white, shrunk it down to a one-inch square, and showed it to
scores of amateur astronomers. When asked to quickly identify the
object, the vast majority responded, "The
Trapezium". Hmmm. Interesting. (AAO photograph of M-45 converted to
black & white). |
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Trivia: What's the nearest star
cluster? Most of those who are moderately
familiar (including us) would be inclined to say the Hyades, at a
distance of 150 light years. But they’d be wrong. The correct answer
is Ursa Major. That’s right – an entire constellation, which is only
half as distant as the Hyades, is actually a star cluster! It’s been
known since 1869 that the Big Dipper itself is actually a group of
associated stars! Many other conspicuous stars are part of this
group as well, i.e.: - Alpha Coronae Borealis, Sirius (Alpha Canis
Majoris), Alpha Ophiuchi, Delta Leonis, and Beta Aurigae, along with
about a hundred others.
With few
exceptions, (notably Alpha and Eta Ursae Majoris) most of the stars
making up the Big Dipper show a common proper motion – a property
typically demonstrated by members of a physically associated group.
In the case of Ursa Major, the motion is to the east and south,
towards a point of convergence in eastern Sagittarius. The group’s
18 by 30 light year area is centered about 75 light years away, and
covers an enormous portion of the sky. For instance, Alpha Coronae
Borealis is 30 degrees away from the group, and is still under the
influence of the Ursa Major Stream, which reaches out beyond a
hundred light years from the cluster's center. Our Solar System is
located in the outskirts but still within the influence of this
stellar stream. |
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TheCoat Hanger
- Collinder 399 - Brocchi's
Cluster Stephen O'Meara says this is one object that actually
looks like what it's called. But for the most part The Coat
Hanger is actually an asterism rather than a cluster. Many of
its members have different (and even opposite) proper motions. We
include it here because it's so popular, and easy pickings in
binoculars and finderscopes. The group spans about 2 degrees. The
rich stellar carpet of the Milky Way makes a great
background. 101mm
refractor
Note that at the southeast end
of the coat hanger's bar is the faint open cluster NGC
6802 (the dim nebulous object to the lower
left). |
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This is a good object
to test your scope AND your vision. NGC 6802 is a dim
object - even in a 10-inch aperture. Much of it begins to resolve
in a 13-inch. This is how it can look in a 24-inch Dob at a dark
site. There are two double stars here that flank the cluster on
the north end. We've been told they were each orange and white. As
you can see, we couldn't bear that out.
24-inch
Dob |
Top..In
Memorium
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