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Old 29-07-2011, 05:01 PM
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esky (Craig)
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First Observation Report 28Jul11

Well thought it's about time I posted an observation report. Been tinkering with the new GSO 12" Dob for a couple of months but this is the first time I've planned what I was going to look at. I decided to give some of the Messier objects a crack as they are pretty good practice before I go off to find fainter fuzzies. Really enjoying the new scope. It's a real gem.


Started observing at around 1900 in my backyard. It was close to the new moon, nice and clear out and just a little wind. I have to put up with the usual street lights where I am but the light pollution isn't too bad. I live near Nelson Bay in NSW. You can usually make out the milky way quite easily, even with a fullish moon. My house blocks the view of the small and large magellanic clouds in the evening, much of the East and the North horizon is fairly blocked by next door.


The eyepiece I used for the following was a 25mm, which gives me a magnification of 60X. I intend to start at the beginning of the Messier list and work my way through in order where I can.


Started with M4. A nice easy Globular Cluster (GC) in Scorpious. At Mag 5.9 it stood out in the finderscope making it quite easy to spot. Through the eyepiece, the stars were resolvable and looked much better than through the small refractor I used to have. GC M80 I noticed was close by so I pointed the scope at it next. All I could see was a smudge, like a small cotton ball of light. M80 was Mag 7.2 and smaller than M4.


Next was M5, another GC but this time in further North in Serpens. A small smudge that appeared dim but stars were resolvable when the atmosphere calmed down. It was closer to the horizon than the previous obs.


Next were M6 and M7. Don't even need the chart for these now. Just look for the scorpion's tail. Great open clusters for small scopes and even better through the 12". M7 is bigger and brighter than M6 and I can notice bright blue stars.


M8 next. The lagoon Nebula. Now I'm pretty sure I got the right one... There's a fair bit going on in that part of the sky I could see a nebula easily and there was a dark lane through the middle. On one side there was a cluster of stars and the other side was dimmer and had just a few brighter stars. Pretty sure it's the right one as it's the first of several brighter fuzzies when you come across from Scorpious. It's a rewarding sight and a nice change from the globulars!


Next was GC M9. Spent ages trying to star hop to get it. At mag 7.9 its barely visible in the finder scope and because its near 2 more dim globulars it a bit tough to figure out if you have the right one. Finally found it after 20 mins of looking. All I could see was a tiny smudge. The 9mm eyepiece didn't show any more detail.


Next were M10 and M12. They are 2 nearly identical globulars, similar size and same magnitude (6.6) and a bit of a challenge to spot. Star hopping is hard since there are no bright ones close by. Stars were resolvable once I found both the GC's.


M11 was next. "Better not be a globular again", I was thinking... Yay, it's an open cluster! Was just above the roof next door at the time of observation. "Wild Duck Cluster? Why do they call it that", I thought? Got the book out and it said it looked like a flock of ducks flying. I could kinda make out a V shape and could see the brightest star in the apex of the V.


Last one of the session was M14, another GC that had me pulling my hair out. There's no really bright stars near enough to it as with M10 and M12. There's a star with a GC 6366 next to it. I was trying to use that as reference but at Mag 10 the globular cluster was probably too dim to spot. Think it was more luck than anything, but I found the little bugger. Magnitude 7.6, reasonably close to next door's roof. Thats enough for one night! Pretty happy with all that so far
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Old 29-07-2011, 10:39 PM
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Paddy (Patrick)
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Sounds like a very good night's star hopping Craig and a very nicely written report as well. You've captured the mood of discovery that goes with a new big scope. I reckon you might find it worth revisiting some of those with a higher power ep. M80 is quite a beauty - very concentrated and a great contrast to M4 (class II vs class IX). Looking forward to more reports.

'Tis a great time of year for GCs!
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Old 29-07-2011, 10:53 PM
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michaellxv (Michael)
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to the obs report section. Nice first report. It's a good time of year for Messier objects and yeah quite a few of them are GC's.
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Old 30-07-2011, 12:33 AM
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Hi Craig & All,

Thanks for taking the time Craig to type up these notes and share them with the rest of us. It can feel a bit daunting to do this first time but you've done really well.

Suggest (after you have found and centred them) using a bit more magnification on the G.Cs to darken the background and make resolving the clusters a bit easier.

M14 is an interesting object that is really stuck out in the middle of nowhere -- hard to hop to. It is also fairly distant and obsured (by galactic gas & dust) somewhat making it hard to resolve. I think the extent of the obscuration is about 2.5 magnitudes. The brightest stars start around the mag 14 mark so unless you observe under dark skies and use some magnification it won't resolve well. It is somewhat larger than average G.C with an absolute magnitude of -9.12 and probably has more than a half-million member stars. In structure, it looks a lot like Omega Centauri (NGC 5139). It is one of the few GC's to host a nova that was discovered many years after the event in a photograph taken by Helen Sawyer-Hogg.


Best,

Les D
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Old 05-08-2011, 05:45 PM
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Esky,Great start.


Regards Orestis
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Old 08-09-2011, 05:35 PM
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madbadgalaxyman (Robert)
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Messier 11 - a Young globular star cluster?

esky,
That was an interesting thought about M11.......the idea that it may be thought of as a globular star cluster rather than an open star cluster.

It turns out that its total mass is about 10,000 times the mass of the sun, which does put it within the range of masses that is found for the globular clusters of the Milky Way and the nearby galaxies.

The distinction between open star clusters and globular star clusters becomes quite minimal above a certain value of the total cluster mass, as the cluster will adopt the characteristic Symmetry and the characteristic Radial Surface Brightness profile (of diminishing surface brightness with radius) that is typical of a globular cluster.(this is called a King profile)

Many other objects containing ~10,000 or more solar masses in the form of stars will also adopt a globular-cluster-like morphology; such as the nuclear star clusters that exist at the very centres of many galaxies.

See the discussion about "High mass open clusters" vs "low mass globulars" (is there a difference?) in the post "Terzan Trio" in the Deep Space forum.

Young Clusters that are very similar to globular clusters (globulars are generally thought to be very old) do continue to form in some galaxies. For instance in the Milky Way, we have the objects NGC 3603 and Westerlund 1. In the Tarantula nebula, we have the cluster R136a .
These objects are sometimes called Super Star Clusters, or massive compact young clusters.

Cheers, madbadgalaxyman

P.S. I never see wild ducks, mythological animals, or any other fanciful outlines in the sky. Generally, all I see are geometric shapes!

The wikipedia entry is pretty confused about the distinction between R136a and R136.....many wikipedia articles make mistakes because a person of limited astronomical background is trying to abstract complex information from the scientific literature.
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Old 01-10-2011, 09:57 PM
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Hi Craig,
And a big welcome to the obs. forum!

GC overload

Wish I had that problem
I take it you were doing a tour using go-to

M4 is one of my favourite objects. It has the most amazing thickening/raised bar of stars through the middle of it Did you see it?
Also, this GC is 70 light years in diamater.... whoa!
Have a look next (if you haven't already) at some loosely scattered GC's- they are strange looking for a GC . Wait.. I'm talking you into more GC viewing.
High power (around 10 to 14mm ep) with a widefield ep is awesome on GC's!

Looking forward to more reports from you.
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Old 02-10-2011, 09:49 AM
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Gem (Grant)
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Thanks for the report! Glad to hear the scope is getting a work out!

I noticed that you were concentrating on Messier objects. There are some nicer globulars that are not "M" objects, if you want to try more globulars... Try NGC 6397 in Ara (easy to find) and NGC 6752 in Pavo.

Well worth the look - they are much brighter than the ones you tried in this report.
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Old 02-10-2011, 09:54 AM
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Gem (Grant)
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As a bit of a "globular tragic", I have been trying to see as many different globulars as possible... with my 9.25" I have seen 79 different globulars so far from the suburbs...
So, with a bit of work your 12" should yield a fine array of objects. Enjoy!
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Old 02-10-2011, 11:24 AM
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madbadgalaxyman (Robert)
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Catalog of Milky Way Globular Clusters

A useful reference for "globular tragics" like Grant, is the "up-to-date and continually updated" list of the Milky Way's globular star clusters ( together with much ancillary data about each cluster) by William Harris, the man who is informally thought of as "Mr Globular" in the professional astronomical community.

This catalog of globular clusters contains an absolute feast of really hot numerical data for each and every globular star cluster, e.g. its position in our Galaxy, its apparent magnitude, its distance from the Sun, the luminosity of the cluster, the foreground extinction, etc.

http://www.physics.mcmaster.ca/~harris/Databases

(If any of the "astro sisters and brothers" have any trouble deciphering this data, I am happy to lend a hand, anytime.)

P.S.
My favourite globular cluster for smaller apertures (3-8 inches) is NGC 6752, because the brightest stars in this cluster are easier to see than in most of the other globulars. I even had some luck resolving it in a 3 inch Refractor, way back when I was 13 years old and the little 3 inch represented the concept of "large and powerful " to my mind!

Last edited by madbadgalaxyman; 02-10-2011 at 11:39 AM. Reason: more info
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Old 02-10-2011, 11:48 AM
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Gem (Grant)
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I simply use "Astrobyte" free software to generate a list of globulars in list of magnitude order and then hit "print screen" button on the computer. There are 100 globulars brighter than magnitude 11.0. It also has the standard description notes, size, etc... I also have a hard copy of NGC 2000 if I want to double check anything. Only one GC in the top 100 has no NGC or IC number - Pal 9 in SGR.

But getting back to the original topic... if you use the above method to generate a list of the top 20 or 30 GC - you should have some nice targets. Comparing to what you observed, M4 comes in at number 8. M80 is about 25 or so.
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Old 02-10-2011, 11:32 PM
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madbadgalaxyman (Robert)
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Grant,

I suppose it all depends on how much a person wants to know about the objects that they are looking at.
For instance, in the aforementioned catalog, we can find the nugget of information that NGC 6522 and NGC 6528 are in a low extinction window which does not have most of the interstellar dust that usually completely hides the very centre of our galaxy from us, and that both of these clusters are right near to the centre of our own Galaxy.

cheers,
Robert
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