Small Wonders: Cassiopeia
A
semi-monthly observing column
By Tom
Trusock – 11/2005
Cassiopeia Widefield
Finder
Chart
|
|
Object
|
Type
|
Size
|
Mag
|
RA
|
Dec
|
|
Targets
|
alpha
|
Star
|
|
2.2
|
00h 40m 51.2s
|
+56 34' 23"
|
|
|
eta
|
Star
|
|
3.5
|
00h 49m 26.6s
|
+57 51' 07"
|
|
|
M 52
|
Open Cluster
|
16.0'
|
6.9
|
23h 25m 06.5s
|
+61 38' 33"
|
|
|
NGC 7788
|
Open Cluster
|
4.0'
|
9.4
|
23h 57m 00.3s
|
+61 26' 11"
|
|
|
NGC 7789
|
Open Cluster
|
25.0'
|
6.7
|
23h 57m 42.3s
|
+56 44' 41"
|
|
|
NGC 7790
|
Open Cluster
|
5.0'
|
8.5
|
23h 58m 42.6s
|
+61 14' 41"
|
|
|
NGC 147
|
Galaxy
|
13.2'x7.8'
|
9.4
|
00h 33m 31.5s
|
+48 32' 34"
|
|
|
NGC 185
|
Galaxy
|
8.0'x7.0'
|
9.3
|
00h 39m 17.7s
|
+48 22' 22"
|
|
|
NGC 281
|
Bright Nebula
|
35.0'x30.0'
|
|
00h 53m 20.8s
|
+56 39' 26"
|
|
|
NGC 457
|
Open Cluster
|
20.0'
|
6.4
|
01h 19m 55.9s
|
+58 19' 29"
|
|
|
M 103
|
Open Cluster
|
6.0'
|
7.4
|
01h 33m 46.3s
|
+60 41' 28"
|
|
|
NGC 654
|
Open Cluster
|
6.0'
|
6.5
|
01h 44m 25.0s
|
+61 54' 54"
|
|
|
NGC 659
|
Open Cluster
|
6.0'
|
7.9
|
01h 44m 48.2s
|
+60 42' 05"
|
|
|
NGC 663
|
Open Cluster
|
15.0'
|
7.1
|
01h 46m 41.6s
|
+61 14' 56"
|
|
Challenge
|
IC 10
|
Galaxy
|
6.4'x5.3'
|
11.2
|
00h 20m 44.3s
|
+59 19' 43"
|
|
|
Maffei 1
|
Galaxy
|
5.0'x3.0'
|
11.4
|
02h 36m 45.8s
|
+59 40' 40"
|
It’s time
to pay homage to
the Queen. In late fall and early winter we see the annual
ascent of Cassiopeia, Queen of Ethiopia, wife of Cepheus and mother
of Andromeda. (This is the rise of the big W in the northern sky
to those
of you less versed in ancient lore, but more familiar with the night
sky.) Although Cassiopeia is a late riser when compared to other
members of her family, there’s little question – at least to this
observer
– that she’s the one in charge. Doubt me?
Well, let’s take a minute
and examine the evidence, shall we? Obviously, compared to
the rest of her family, she’s a late riser. That’s a given.
While poor old Cepheus is up and about the business of running the
kingdom, she hasn’t even peeked above the horizon – no, she gets to
sleep in. And then there’s the whole chair bit. She’s the
only one in her entire family that’s seated! Now, my wife tells
me it’s because she’s been up all night with the children, but in my
book, poor old
Cepheus has been up just as long and he’s forced to stand!
Finally – as if you need more evidence – just take a look
at her jewelry. Cassiopeia, being smack dab in the middle of the
winter milky way is a true treasure trove for all sorts of flashy
ornaments – and it’s those that we’re interested in tonight. She
does get her comeuppence of a sort – while sitting in the chair, half
the time she finds she's upside down. According to some sources
this is
punishment for her boast that she was even more pleasing to the eye
than the sea nymphs. Ahh, vanity.
Well, on to the celestial
targets. First off, we’ll take a
look at a few of her solitaires: Alpha – better known as – Schedar, Eta
– or Achird, Gamma, Iota and – well, what was once one of her shining
jewels - Cassiopeia A.
Schedar is
the brightest
star in Cass, although not by much and not all the time as it can be
surpassed in brightness by the variable star Gamma. Gamma itself
is unique as it’s held by some to be a binary star system that contains
a Be star and a neutron star and is the brightest x-ray binary star in
the night sky – to my knowledge no other x-ray binary can be seen with
the naked eye.
Trivia – the first
voyagers to the Centauri star system will see Sol near epsilon at about .5 mag in brightness.
Achrid is a
well known
binary that the NSOG informs us was discovered by Sir William Herschel
in August 1779, the period is around 500 years, and the separation
varies between 5” and 16”. It’s purported to see be
multiple colors – heavily dependent on the aperture you use to view it
with. Take a look for yourself.
Cassiopeia A (RA 23:23.4,
Dec +58:50) is the youngest known supernova remnant in our galaxy
having exploded sometime around 1667. Opinion on who was
the “discovery” observer is divided – some feel that John Flamsteed
cataloged it on August 16, 1680 – others point out that the “star” he
cataloged has nothing exactly corresponding to it’s position, and that
he simply made an error. Other than that, the first time it
stepped into the limelight was in the late 1947’s when it was cataloged
as the strongest radio source in the sky (excluding solar system
objects) and given the designation Cassiopeia A and received the
designation 3C 461 in the third Cambridge survey. While it’s not
a visual target per-se, it is a fairly interesting object located in
Cass.
 Iota is a challenging triple,
namely in seeing how small of an aperture and low of a magnification can split it – take a
minute if you have clear skies and give it a go. Here’s an image
contributed by Simon Walton - one of our longtime readers. You can get an idea of the main difficulty you'll be facing. Iota's actually a triple star. To give you an idea here, the magnitudes are 4.5, 8 and the closer companion is listed as mag 7 (you'll probably need at least a 4" to see all three).
While her
stars are
interesting, there’s no denying that they are far from the only
attraction. Cass is rich in targets, particularly open
clusters. What else would you expect? These are
the spectacular, shiny objects that favored of a
queen. Other targets? A search of the database reveals that (brighter
than mag
13.5)
there are: 7 galactic targets, 1 quasar, three planetary nebula
(the brightest IC 289 at mag 12.3), 4 “bright” diffuse nebulae,
138 dark nebulae, and 43 open clusters. Clearly there’s plenty
here to
keep an observer busy for a LONG LONG
time.
For the DSO’s this month,
we’ll start with the western edge of the W, and follow along hitting
our targets as we go. Just a few short degrees from
Beta, we find three objects worthy of telescopic inspection.
First up,
we’ll stop at
NGC 7789. This has to be one of my all time favorite open
clusters. Ok, sure, you probably hear me say that nearly every month,
but hey –
it’s true! And doubly so this time. This object looks
amazing in nearly any size telescope. I’ve viewed it with scopes
as small as 60mm refractors to monster 20
inch dobsonians – and they all had something to offer. Smaller
scopes can
expect a mist that breaks into pinpoints of light as
conditions or aperture increases. Large scopes can see hundreds
of individual stars that, to me, have a very evident rose or whirlpool
effect – although to the best of my knowledge, I’ve never heard any
other observer describe it that way. If you have a large scope,
please take a look and tell me what you see. Is this simply my
overactive
imagination at work? Or is my brain pulling out a subtle pattern
but existing pattern? Intermediate scope users most likely
won’t see any sign of the whirlpool, but they will see an extremely
rich concentration of both resolved stars and the background mist that
indicates hundreds more lying just beyond the resolution limits
of their equipment.
This cluster should be
visible with any form of optical aid, and I’d suspect you could even
see it naked eye from a suitably dark and transparent site.
Anyone care to put
this theory to the test?
Eric Graff’s
wonderful
sketch is an excellent depiction of what to expect through a 4-6 inch
telescope from a moderately dark site.
 Next, lets head just
north, and over to a
chain of clusters – the two brightest being NGC 7790 and NGC 7788.
As you can
see, there are
a total of six clusters in the immediate area, five of them in a
chain. For the small scope user, simply concentrate
on finding 7790 and 7788. These two clusters are the brightest in
the chain and will probably be seen as a general mist with a few
defined stars from a moderately dark site in a small telescope.
The other clusters I’ve
found to be more of a target for larger telescopes, detailed
maps and much patience. Frankly, I’ve often had a difficult time
picking open clusters out of the Milky Way background – it’s sometimes
difficult to tell where one cluster leaves off and the background
begins.
Spend some
time here and
see how many you can make out.
Dropping further west, we
come to one of the two Messiers to be found inside the Cass border –
open
cluster M52.
According to some of the
latest astrophysical data, M52 is some 20 million years old, measures
24 or so light years in diameter and contains over 200 members.
Telescopically, I find M52 a very rich, very pretty star cluster.
M52
and the Bubble Nebula –
Contributed by Dean Rowe
If you see a
faint glow
in the area, you aren’t imagining things – no, just a few arc minutes
southwest of M52 we find the Bubble reflection nebula (NGC 7635) – make
sure to take a look for this if you’re observing from dark skies with a
large scope. Take a few minutes and try a UHC filter to see if it
improves the view.
After you’ve finished,
let’s head back to the W and move east.
Forming a
triangle with Alpha and Eta, we
find the emission nebula / open cluster NGC 281. In smaller
scopes look for hazy glow. Exactly what this is, I'm not
positive. It's either the unresolved cluster, or the
nebula itself. I’ve never been able to determine. Larger
telescopes begin to show stars associated with the cluster, and again,
I’d
recommend that you try a UHC filter to see if it enhances the contrast
and helps to better define the nebulosity.
NGC
281 – Ralph McIntosh
Unfortunately, we can only imagine seeing it
as Ralph McIntosh has captured it.
Once you have found 281 do take the time to
inspect it in detail. So many observers today are of the GOTO
tourist variety. You know what I mean - Plug in the numbers, slew to the target,
take
a quick peek and on to the next we go. That’s a disservice
to
nearly every target – and this one in particular. Try it filtered
and unfiltered. Use different eyepieces and vary the
magnification – look for unevenness in the nebula – bright and dark
patches. Do you see stripes? Knots? Whirls? Or is it
uneven and featureless? Spend some time here and take some notes
about what you
observe. When you’re ready, move east again, this time to NGC
457.
Variously called the ET, Alien, Ghost, or
Airplane cluster, this is a wonder that Messier somehow missed and a
sure
favorite at fall star parties. I tend to see it as either
an alien or an airplane. The two bright stars at the top right of
Eric’s drawing serve as either the eyes or the engines. The
scattering of stars just below them are the outstreached arms or the
wings, and the body continues on down.
Reader Brian Carter has this to say about
observing 457 in a 10” Dobsonian:
To me it is
an almost perfect replica of the Gemini constellation. the 2
dominant stars, maybe 8-9 mag, are in the same position as Castor and
Pollux. Other stars make up the respective legs and arms of the
twins. There are a number of 'dark' red stars, like dim carbon
stars. This is one of my favorite clusters, really stimulates the
imagination.
I remember the very first view I had of this
cluster, oh-so-many years ago. I stumbled upon it with my 8”
dobsonian, had no idea what I was looking at, but must have spent an
hour simply staring at the view.
Personally, I find this probably the most impressive cluster in Cass –
for a small telescope anyway. Although 7789 gives it a real run
for it's money.
If you’re interested in reading more about
this cluster, I highly recommend The Caldwell Objects
by O’Meara.
For reference, NGC 457 is Caldwell #13.
Moving on down the W, to the NE, just off
Delta, we find
Messiers other object for Cass – well, technically, I guess it’s not
REALLY Messiers – as in Messiers find anyway, but it is entry 103 on
the
Messier list. Discovered by Messier’s friend Pierre Mechain in
1781, ironically, this is the last object in Messiers’s original
catalog. In the past, there’s been some debate as to the
genuineness of this open cluster, some have seen it as a random
association, but modern data tends to confirm
its existance as an associated group of stars. Personally, I find
that M103 is best viewed at low powers and in
small scopes. Large aperture and high powers tend to overwhelm
the cluster and it looses it’s attraction.
M103 -
Jeremy
Perez
I particularly like Jeremy Perez’s sketch of
M103. In my opinion, a nice low power view that shows the
surrounding area well is
the best way to view this cluster. With it’s distinctive
triangular shape, some observers have called it the Christmas tree
cluster, but that’s never been really apparent to me. An
ornament, perhaps – especially with the colorful stars scattered
throughout and nearby. Either way, let it serve as a reminder
that very very soon many of us will be clearing
off the residue from a massive turkey dinner and hauling out all those
Christmas decorations. Heck, I don’t know about you but the Wally
World by me has all of the Christmas stuff out already.
Lets move NE again, and this time we’ll come
across a
nice collection of clusters – 663, (The horseshoe cluster), 654 and 659
are the three dominant, but there are a plethora of others scattered
throughout the
area. As you can tell from the wide field composite DSS image
above, this is a very crowded area and certainly deserves some time
with a small (or large for that matter) telescope. The two most
interesting clusters in the photo above, I find to be M103 and NGC 663,
but the others are worth a visit too. In fact, if you have a wide
field scope, pop in your widest eyepiece, take out a chart and just
spend an evening seeing what you can spot in this (and surrounding)
area(s).
NGC
663 – Jim Thommes
Finally, we come to a few extra-galactic
targets. Consult the wide field map and head back to the other
end of Cass where we’ll literally go off the deep end for these
two. Then use the chart just below to help narrow the field.
 Talk
about Andromeda’s satellites and people think M32 and M110 – well,
they’re missing two others that can easily be spotted in a small scope.
Well, we'll go off the beaten path a bit to
show you a couple more: NGC 185 and NGC 147.
Separated by about a degree, a sufficiently
low power and wide field will show both of these in the same
view. While they are somewhat small (at least compared to M31),
they are also surprisingly
bright. I’ve managed to pull both out in a small scope from a
dark site on an excellent night, but I’d go so far as to recommend a
6-8” telescope would be more the norm for these two for observers
working under "typical" conditions.
Don’t expect a lot of detail – like most
galaxies, there just isn’t any. They are two little puffs of
intergalactic
cotton. Your reward is seeing some little known extragalactic
satellite
galaxies for one of the most popular deep sky targets ever. I’d wager
that few amateurs even know these exist, and fewer still grasp the
significance.
Challenge objects:
There are two more galaxies this month – one
shouldn’t be
particularly difficult, but I think I hit it on a poor night, and am
therefore placing it in this category.
That one, the first, is IC 10.
A faint but definite blob in the 18” at
around 250x, the poor conditions made me think that this would probably
be a fairly easy catch on a different night. So, your homework
assignment - What’s the smallest
scope you can grab IC 10 with? Please note all the details -
conditions, eyepiece (type and focal lenght please) and, of course,
size of the telescope.
The other challenge object this month is a
little harder, but - at least to me - vastly more interesting.
Oh, not for what you can see, but what it is.
Maffei 1.
 Found
near the Perseus border, Maffei1 is the largest galaxy in the Maffei 1
galaxy group (also called the IC 342 group). These lie very
close to the galactic plane and thus tend to be obscured by heavy
amounts of galactic dust and gas. The (major) known group members
include IC 342, Maffei 1, Maffei 2, Dwingeloo 1 and Dwingeloo 2, with
additional candidates suspected.
According to SEDS, W.E. Denning discovered
IC 342 in 1895, Paolo Maffei discovered Maffei 1 and 2 in 1968, while
Dwingleoo 1 and 2 were discovered in 1994 and 1995 respectively.
The Maffei 1 group was probably once a
member of the local group, but was ejected because of an encounter with
M31. Since then, they have moved out to about 10 million light
years distant and continue to move away. If it weren’t for the
intervening gas and dust in the Cassiopeia Milky Way, this giant
elliptical would probably be one of the most spectacular galaxies in
the night sky. That we can see it at all, is a testiment to it's
greatness.
If you go after Maffei, do it with as much aperture as you can get your
hands on - I'd suggest a minimum of 12-14 inches. Sucessful amaterus
stress that you need to; ensure you have good charts and be prepared
for some haze with a small group of foreground stars. It's
too easy to think you're looking at an unresolved (or partially
resolved) galaxy and not a largely unresolved cluster.
This is one of those targets, not so spectacular for the views it
provides, but for what it is.
Betcha didn’t think a mere 10 million light
years would get you out of the local group of galaxies, eh?
A special thanks to all who contributed this
month – there were many, and picking through photos, and sketches is
always enjoyable – I only wish I could use every image and description
that was sent in.
Well, that's pretty much it for this month. I know, I know
there's a lot more I could have covered, and if you saw the initial
list, there was a lot more I thought about. I'm sure I skipped a
lot of amateurs favorite targets - If you find yourself wanting more,
here are a few suggestions (not exactly applicable to all telescopes -
do your research first ):
Additional Targets in
Cassiopeia:
|
Eta Cass
W Cass
Stock 2
Stock 5
Stock 12
Tr 15
NGC 7635
NGC 436
|
NGC 146
NGC 225
NGC 275
NGC 129
NGC 278
IC 289
Q0241+0061
Abell Galaxy Cluster 63 |
And those should give you an additional night or two of observing.
Till next time –
Clear Skies!
Tom T.
Additional
Reading/Resources:
Cassiopeia A and Supernova 1680 or 1667
http://www.seds.org/~spider/spider/Vars/casA.html
The Maffei 1 Group of Galaxies (also IC 342 Group)
http://www.seds.org/messier/xtra/ngc/maffei1g.html
Small Wonders Home Page (More SW here):
http://www.cloudynights.com/category.php?category_id=101
I'd love to hear of your experiences under
the night sky - please feel free to
e-mail me or send any observing reports to: tomt@cloudynights.com
Please indicate if I can cite your observations in future columns.
Photographic Images Courtesy DSS: copyright notice
http://archive.stsci.edu/dss/acknowledging.html
Star Charts Courtesy Chris Marriott, SkyMap Pro 10 Printed
with Permission
http://www.skymap.com
Special Thanks to Collin Smith for his editorial assistance,
Olivier Biot for assistance with the PDF’s and all those who take the
time to read and contribute to this series.
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