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(This article originally appeared in the Q4 1999 STAR newsletter. -Ian)
Indulgence
in Obscurity
by
Eric Honeycutt
The
following is a scenario that I would like to present and see if it
sounds at least somewhat familiar to you: It is a Saturday evening in
late January. Temperatures are hovering around freezing and Greg
Fishel promises that skies are going to be "clear as a bell",
dew points and humidity are going to be extremely low, and water
vapor imagery shows a large, black "hole" over NC. Your
SCT is calling your name from the garage while your spouse willingly
tells you to "go ahead" while out of the blue, gives you a
brand new Tel Vue 35mm Panoptic as a mere "gift of love"
(go with me here). A situation such as this is considered a rarity
(to say the least) but even under such ideal conditions, there are
some out there who would still think twice about going out to
observe. Why? When you look into your coming night's future, what
do you see? M42, M42, M31, maybe The Double Cluster and a few bright
NGCs? Do you anticipate a night of advancement into this wonderful
hobby (lifestyle) or are you planning on well, idling in the same
objects you have observed too many times? Sure, these objects do
warrant repetition but do you feel yourself possibly losing the
slightest amount of interest simply because all that you might think
this hobby (lifestyle) has to offer is fainter and less detailed
objects than the ones you might be overly-familiar with? I am here
to say that if it hasn't happened yet, more than likely it will to
some degree. If this persists, you will find yourself just looking
blankly into the sky after a mere few hours of observing, wondering
what else there is worth pursuing and you can think of nothing
exciting! Suddenly you realize that the motivation you had as
beginner is fading. Now, a warm bed and sleep begin to really sound
good as the cold, damp, heavy dew, and high humidity of a partly
cloudy night envelop you. But now you have to spend fifteen to
thirty minutes (or longer) taking down the equipment and packing the
car. Another hour later you arrive at home and you realize that you
didn't sample any new objects at all and wonder why you even bother.
Sound familiar?
I
use to be there. That was until I realized that if you do a little
research, you can find some fantastic objects up there that show as
much, if not more detail than many of the well-known NGCs and yes,
even Messiers. If you know anything about me, you know that I will
pull up some objects in my 22" that are quite obscure. Names
like Perek-Kohoutek, Sharpless, Minkowski, Hickson, Abell, Arp,
Semeis, Brochum, Mellotte, and Dolidze-Dzimselejsvili are common
entries in my observing logs. Once I actually started observing some
lesser-known NGCs', ICs', and some of the obscurities mentioned
above, I immediately found that there were some great objects up
there worthy of attention. Not only that, I was utterly amazed that
I had never read nor heard about many of these great objects from
S&T, Astronomy or astro-aquaintences. Suddenly, a sense of
excitement and purpose began to accompany my astronomical pursuit and
I could honestly say that I looked forward to every single clear
night I could get out and yes, this was still with an 8" f/6
Meade Starfinder, not a 22" f/4.1 Starmaster. Thus, I want to
share some of these gems with you.
I
am going to present a list of my winter favorites that you may or may
not have heard of. All should be in reach of an 8" telescope
but they do require "Big Woods skies" or preferably, darker
to reap the best views. Also at the end of this article, I will post
some "challenge objects" that should test even the most
seasoned veterans. I would also like to hear of your observing
reports if you do go after some of these so please e-mail me or post
them on the RAC website. If you are someone who is starting to
experience "astronomical burn-out", hopefully this list
will help motivate you. This will be a relatively long and detailed
list to keep you nice and busy until the Spring sky arrives at a
decent hour in a few months.
First,
lets start in a constellation well known for deep sky objects (in
which I will now abbreviate by "dso") especially open
clusters and faint nebulae, the constellation of Cassiopeia the
queen. To start things out easy and to hopefully motivate pursuit of
the "Herschel 400", I chose some objects from the list to
wet your appetite. Awhile back when nebula filters were starting to
become popular, I bought a UHC filter. One of the very first objects
I used this particular narrowband filter on was NGC
281.
This Emission Nebula/Open Cluster was surprisingly bright haze
enveloping a loose open cluster (actually 2 clusters are associated;
the other is IC
1590
so you can bag an IC object as well). The nice thing about this
emission nebula is an obvious dark notch within the nebula but it
will take a UHC or O-III filter to spot. The notch is wedge-shaped
and is quite a treat in 12" or larger instruments as "horns"
extend from the dark nebula. NGC 281 is an easy find as it is just 2
degrees NW of Schedar (Alpha Casiopeiae).
The
next object we shall look at is IC
1747.
One thing that I was amazed to discover when I was advancing through
my beginner phase was the number of IC objects obtainable in my 8"
scope. IC 1747 is one of them. This is a planetary nebula that
requires an O-III or UHC filter to be seen well. It is an easy find
as it is 30" SE of the 3.4 magnitude star Epsilon Cassiopeia.
The PN is 13" in diameter which means it is not stellar unless
viewed at low power. I suggest you use the blinking method with your
nebula filter to find it if you have trouble locating it. It should
not be difficult as its visual magnitude is 12.1.
Keep
that narrowband filter on and go to NGC
896.
This 20' x 20' nebulous patch is a relatively bright, oval glow but
might be difficult without a UHC or O-III filter. Try to notice a
dark lane in the nebula. If you notice a slight division, the other
side of the division is actually IC
1795
and should be visible under dark, transparent skies. These two
nebulae are a great sight for large aperture scopes as a plethora of
dark nebulosity can be glimpsed within the glow of the emission
nebulae with a UHC or O-III employed.
Our
next gem in the queen is the beautiful and rich open cluster NGC
457
so you can take that nebula filter off now. Lying at 9300 light
years away, this object is easily found by when you find the gorgeous
double star, Phi
Cassiopeiae
(its membership with the cluster is not known for sure). The double
is a yellow and blue star with the separation of 134" and lies
to the SE edge of NGC 457. The cluster has roughly 50 stars visible
within the 8". The concentration is moderate with arcs and
chains of stars curving through the middle of the cluster from either
side of the double star.
Next
is NGC
7789,
a magnificent open cluster of several hundred 11th magnitude and
fainter stars. It lies 5900 light years distant and is estimated to
be 2 billion years old., very old for an open cluster but young for
the more populated globular clusters. It is amazing that Messier
never included this one into his original list or his predecessors
who later expanded the list to 110 objects. The great thing about
observing this OC is how it's thick concentration of stars disperses
outwards into a rich, surrounding starfield. It may be hard to
determine where this one ends because of all the stars encompassing
the halo. The center of the cluster in an 8" in an unresolved
haze.
Our
last object in Cassiopeia is another fine open cluster. NGC
663
is a grand assemblage of stars. The cluster is quite rich and
beautiful in 16' of space. 80+ stars make up this cluster and there
are 3 labeled double stars in the cluster as well (Sigma
151, 152, and 153).
For added detail, see if you can notice the dark streak running
through the center of the cluster.
Now,
lets go south a little ways into the hero, Perseus. This
constellation contains such favorites as the Double Cluster, M76,
M34, and The California Nebula. But there are many more objects that
many amateurs are unaware of. Since you still have that nebula
filter off, lets take another look at a great open cluster, NGC
1245.
This rich cluster is a splash of 80 stars in a 10' area. For
detail, you will notice short star chains and arcs throughout the
cluster. Very nice.
Now
back to the nebula. One of my favorite objects in Perseus is the
emission nebula NGC
1491.
It is often overlooked unless
you are someone who thinks that you are about to be responsible for a
bright comet discovery because this dso looks exactly like a comet!
So before calling CBAT, make sure you know it is not this neat
little nebula. An 8" will show a bright, fan-shaped glow
resembling a stubby-tailed comet. For detail, look for tapered
edges at the end of the "tail".
Keep
on the nebula filter and lets go for another IC planetary nebula.
This one is IC
2003,
a 7", 12.5v magnitude disk. Now, since this one is only 7",
blinking with a nebula filter becomes necessary unless you already
know exactly where to look. Once you blink the nebula into
confirmation, use 200x or higher so that the stellar image turns into
a disk. Once you see the PN as a disk, see if you can detect the
13.5 magnitude star which is just 15" to the SW.
Our
next dso is a new object for this list. It is a reflection nebula
and its designation is NGC
1579.
It is a medium brightness glow that is oval in shape. For the
beginners, a nebula filter does not help the observation of
reflection nebula; it hinders the observation because reflection
nebulae are nothing more than reflected starlight off of a dense
cloud of molecular hydrogen and dust (this gas and dust is nothing
more than dark nebulae; it’s just that now we can see the dark
nebula because of a nearby or embedded star). Emission nebulae
actually emit their own light when hot young O and early B-Type stars
excite the surrounding local gas clouds through ultraviolet
radiation, hence causing the ionized gas to fluoresce. Nebula
filters highlight the excited gas (note: narrowband filters simply
allow the wavelengths of light indicative to emission nebula to pass
while severely limiting all other wavelengths; the only way a filter
would work for reflection nebula would be to invent a "starlight
filter" that blocks out all light other than the wavelengths
indicative to starlight - a concept that is currently being
researched for the possible advent of a filter specifically designed
to see faint central stars in planetary nebula while blocking out the
nebulosity that surrounds that central star). Back to our object,
see if you can detect a fainter, nearly separated glow to the west of
the main oval nebula. This is not a separate designation since the
nebula is not actually divided. Detail can be glimpsed but since we
cannot take advantage of a narrowband filter, dark skies become
absolutely imperative.
Our
next stop is a quick turn off into Monoceros, the unicorn. Though
many great objects lie here like M50, NGC 2337-39 ( The Rosette
Nebula and associated cluster) and NGC 2261 (Hubble's Variable
Nebula) and some great NGC open clusters, I want to simply point out
a planetary nebula with a conspicuous central star that is also
variable in nature. This PN is is NGC
2346 (Minkowski
1-10).
An 8", an O-III filter, and power over 175x will help you see
this greenish-grey PN as somewhat box-shaped instead of circular or
amorphous which is peculiar to so many planetaries. The central star
varies in magnitude from 11.3 to 13.5+ but is usually visible at high
power when seeing is steady (don't forget to remove the O-III to see
the central star if it is not readily apparent with the filter
employed).
Speaking
of prominent central stars in conspicuous planetaries, I now
introduce NGC
1360
for those who may have never heard of this one before. We have to
jump far into the southern hemisphere, namely the constellation of
Fornax the furnace. There is a planetary nebula so large and so
oblong, one could easily mistake it for a galaxy with a prominent
stellar nucleus. That stellar nucleus is actually a central star
with the super-bright magnitude of 10.9. The nebula itself is a
whopping 9'x5' monster (huge for a PN!). Larger apertures show dark
streaks and subtle uneven texture within the nebula. This one is
always a surprise when first observed and a pleasure to observe.
Have
you ever observed an extragalactic globular cluster? This is a
globular that is associated with another galaxy other than our own.
There are quite a few visible in M31 and M33 that aren't too
difficult to track down but will require some time to find initially.
There is also NGC 2419, also called the "Intergalactic
Wanderer" but this is a globular currently believed to once have
been apart of our galaxy. However, with its current distance of
300,000 light years away from our solar system (out beyond the
Magellanic Clouds) and has a true space velocity greater than our
Milky Way's escape velocity, obviously the globular has been shoved
away from us and is traveling into the interstellar voids between the
galaxies. Yet, the globular that I present here is NGC
1049,
still in Fornax is truly a member of another star system. It is
associated with the Fornax Dwarf System which will be invisible to
most amateur instruments so don't bother hunting for it in an 8"
scope. At visual magnitude 12.6, its not hard to get excited knowing
that you can observe an extragalactic globular but beware, the
surface brightness is lower than 12.6 and can be faint in an 8"
(yet bright enough to warrant its own NGC designation). Make sure
you are under dark skies and observe this object when it transits
across the meridian. With a little patience, it is rather easy when
you know you are observing it. Good luck!
Speaking
of globulars, get ready for a show stopper! We are going to go east
from Fornax but stay very low in the sky. There is a constellation
bordering Lepus and Canis Major called "Columba", the dove.
Many do not realize that there is a deep sky splendor there so
large, so bright that if it were just 10 degrees north in declination
it would surely be Messier 111. The globular is NGC
1851.
This is a beautiful globular cluster that is often overlooked because
of its obscure location. You will need a very low southern horizon
(Big Woods will do) and catch this on the meridian and you won't be
dismayed. The object has a bright, condensed core that is
unresolveable in an 8". However, the outer periphery is laced
with many 10th and 11th magnitude stars. Larger scopes show a
mostly-resolved core and very bright individual stars all around the
edge of this fine globular. I will check this one out at The Winter
Star Party later this month and update my notes.
Going
northeast into Canis Major, there are a few bright nebulae that are
worthy of your attention. The first is NGC
2359 also
known as "Thor's
Helmet"
or "The
Duck Nebula".
This one and many other bright nebulae are often overlooked because
of the many open clusters Canis Major has to offer. A UHC filter or
O-III will help this object greatly. In smaller apertures, this
emission nebula resembles a duck's head and bill (larger instruments
show detailed extensions and a wealth of detail). Definitely put
this one on your list, you won't be disappointed. Another bright
nebula lies close to NGC 2359 and it does not have a NGC designation.
Rather, it is from the Sharpless catalogue:
Sharpless 2-301.
A narrowband filter is a necessity for this one, preferably an O-III
filter. An 8" will show a faint but triangular glow 6' to 8'.
Several stars are embedded in the nebulosity, one of the brighter
objects from the Sharpless Catalogue. An open cluster worthy of a
observation is NGC
2362.
It is easy to find because it surrounds the 4th magnitude Tau Canis
Majoris. It is a rich, compact cluster. The cluster lies out at
about 5,000 light years and its diameter is roughly 8 light years
across. Tau Canis Majoris is the brightest member of the group (yes,
believed to be a true member). The observation will prove to be
rewarding as the cluster is very bright, rich, and large in diameter.
Tau CMa is truly odd being so bright.
Over
to Puppis, the ship's stern now for a nice emission nebula and open
cluster: NGC
2467 (also
known as Sharpless
2-311).
The object is an easy, oval glow with a UHC or O-III filter, even
in a 5" scope. Internal darkening is discerned even in a 5"
but with more certainty in larger instruments. Also, larger
apertures show outer areas of nebulosity not apparent in scopes under
10". Nice surprise. Also in Puppis, there is a nice planetary
nebula that also might be overlooked. NGC
2440 is
a medium-sized planetary (32") who's greenish, oval disk is
readily apparent at powers over 175x. The magnitude is an easy 9.4
visual magnitude so it shouldn't give you much problem. Of course,
you should always check out the beautiful planetary superimposed over
M46 while you are in Puppis but most have heard of this object so I
won't devote the time.
Now,
you may be wondering why I haven't gone to Orion yet. Well, there
are so many bright NGC's and of course, the famous Messiers that are
known because of the popular constellation and/or the objects are
listed in the Herschel 400. Thus, I am not going to analyze any
particular object except to briefly list a few favorites. These
objects include NGC
1973-75-77, NGC 2024, NGC 2023, NGC 2022, IC 434 and Bernard 33 (The
Horsehead), and NGC 2174. All
are worth observing but even though all are visible in an 8"
scope, most of these require 10" or larger instruments to
discern appreciable detail.
I
hope I have offered some objects that are a little more off of the
beaten path. These objects are not just faint fuzzies. Instead, I
chose these gems because of the detail that can be glimpsed under
good conditions. We have a few months to observe these deep sky
objects so don't feel as if you have to observe them all in one or
two nights. They are to be absorbed slowly, like a fine glass of
wine. I want to hear about your observations so please post them on
the RAC website. Here are the data for all the objects listed above
to make the hunting easier:
Object
|
Cons
|
Type |
Mag |
Size
|
R.A. |
Dec
|
| NGC
281 |
Cas |
EN/OC |
7.4p |
4' |
00h 52.8' |
+56° 37' |
| IC
1747 |
Cas |
PN |
12.1v |
13" |
01h 57.6' |
+63° 20' |
| NGC 896 |
Cas |
EN/OC |
Ph
Br 1-5 |
20 'x 20' |
02h 26.5' |
+62° 04' |
| NGC
457 |
Cas |
OC |
6.4v |
13' |
01h 19.1' |
+58° 20' |
| NGC
7789 |
Cas |
OC |
6.7v |
15' |
23h 57.0' |
+56° 44' |
| NGC
663 |
Cas |
OC |
7.1v |
16' |
01h 46.0' |
+61° 15' |
| NGC
1245 |
Per |
OC |
8.4v |
10' |
03h 14.7' |
+47° 15' |
| NGC 1491 |
Per |
EN |
Ph Br
1-5 |
25' x 25' |
04h 03.4' |
+51° 19' |
| IC
2003 |
Per |
PN |
12.5v |
7" |
03h 56.4' |
+33° 52'
|
| NGC 1579 |
Per |
RN |
Ph Br
1-5 |
12' x 8' |
04h 30.2' |
+35° 16' |
| NGC
2346 |
Mon |
PN |
11.8v |
60" x 50" |
07h 9.2' |
-00° 48' |
| NGC
1360 |
For |
PN |
9.4v |
9 'x 5' |
03h 33.3' |
-25° 51' |
| NGC
1049 |
For |
GC |
12.9v |
0.4' |
02h 39.7' |
-34° 17' |
| NGC
1851 |
Col |
GC |
7.2v |
11' |
05h 14.1' |
-40° 03' |
| NGC 2359 |
CMa |
EN |
Ph Br 2-5 |
9'
x 6' |
07h 18.6' |
-13° 12' |
| Sh2-301 |
CMa |
EN |
Ph Br
1-5 |
8'x7' |
07h 09.8' |
-18° 29' |
| NGC
2363 |
CMa |
OC |
4.1v |
8' |
07h 18.8' |
-24° 57' |
| NGC 2467 |
Pup |
EN/OC |
Ph Br
1-5 |
16'x12' |
07h 52.5' |
-26° 24' |
| NGC
2440 |
Pup |
PN |
9.4v |
32" |
07h 41.9' |
-18° 13' |
Listed
below is my challenge list. Some of these objects should not be
attempted if you are pregnant, have heart problems, or cannot handle
intense levels of stress. Good luck!
Eric's
Challenge Objects:
The following objects are for die-hards with keen eyes, good
skills, and apertures over 12":
| IC
423
|
Reflection Nebula in Orion |
| IC
426 |
Reflection Nebula in Orion |
| Bernard's
Loop |
Hold 2" O-III filter up to your eye in very dark skies to
glimpse this very long nebula. |
| Abell
10 |
Planetary Nebula in Orion |
| Abell
12 |
Planetary Nebula in Orion (just 2' wnw of mu Orionis) |
| Minkowski
1-18 |
Planetary Nebula in Puppis |
| Abell
22 |
Planetary Nebula in Gemini - "The Medusa Nebula" |
| IC
443 |
Super Nova Remnant in Gemini - "The Winter Veil" |
| Semeis
147 |
Super Nova Remnant in Taurus |
| IC
405
|
The Flaming Star Nebula |
| Sharpless
2-221
|
Super Nova Remnant in Auriga |
| Sharpless
2-216 |
The Closest Known Planetary Nebula (Retinal torture) |
| IC
1613 |
Dwarf member of Local Galaxy Group (Large apertures in ultra-dark
and steady skies may reveal individual stars within this close but
faint galaxy). |
| Jones-Emberson
1
|
Large Planetary Nebula in Lynx |
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