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Observing >> Deep Sky Observing

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Niels2011
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Visualising large scale structure in the night sky new
      #5876540 - 05/21/13 06:03 PM

Tom Jarrett's Large scale structure in the local universe

I came across this web page with these great all sky images, including a poster, based on the 2MASS XSCz survey catalogue of galaxies out to z=0.1, in shells with increments of z=0.01. It's really helpful for visualising the large scale structure of the local galaxy clusters, superclusters, walls, filaments and voids from a perspective of looking up at the sky, and putting the galaxies we observe in the context of these larger structures.

Very possibly this has already been linked on CN, and if so maybe it's okay to post it again because not everyone will have seen it, and I hope you enjoy it.

These findings were also reported in this paper: Jarrett, T. (2004)


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GlennLeDrew
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Re: Visualising large scale structure in the night sky new [Re: Niels2011]
      #5877732 - 05/22/13 10:47 AM

I derive much greater satisfaction in visualizing the structure of our very own Milky Way galaxy. To me, external galaxies have essentially *absolutely nothing* to do with the arrangement of the stars, associations, clusters, nebulae and dark clouds which comprise our own intricate and fascinating galaxy.

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Niels2011
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Re: Visualising large scale structure in the night sky new [Re: GlennLeDrew]
      #5880567 - 05/23/13 03:50 PM

Yes, of course I agree about the beauty and intricacy of our galaxy. I went to a great talk on Monday night by a visiting astronomer called 'The science and beauty of nebulae" - lots of great images of star forming regions and explanations of the science behind the images.

Lately I have been doing a lot of galaxy observing, and I have got interested in the large scale structures which galaxies are a part of. Also maybe because from my mag 5 skies and with an 8" newtonian almost all DSOs are faint fuzzies, intra galactic or extra, and even though I can't see structure in almost any of them, there is visible structure in their 3D relationship in space. A few weeks ago I got lucky with clear nights after a long cloudy winter and I traced a wandering line of 56 galaxies from UMa to the centre of the Virgo cluster. Now I'm thinking of checking their distances and getting more of a picture of distance as well as angular separation - which might be fun on a cloudy night.

Anyway... So I was wondering what other people's experiences and thoughts were with observing these larger-than-galaxy structures, and any hints and tips eg observing the Great Wall etc. ?


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GlennLeDrew
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Re: Visualising large scale structure in the night sky new [Re: Niels2011]
      #5881486 - 05/24/13 01:10 AM

That there seems to be little interest in the subject of large-scale structure in the distribution of galaxies is indicative of the topic's inability to fascinate. I can see why. We are considering what are effectively isolated, non-interacting concentrations of mass in a largely empty void. And where interacting, the tIme scale is of order a billion years. How boring!

Indeed, when considering such isolated specks of mass in a sea of essentially nothingness, trying to assemble the larger picture in the mind's eye is difficult at best.

Within our own Galaxy, where, moreover, small instruments can be brought to bear, we observe a *very* much wider array of objects in close proximity which interact on vastly smaller time scales. Much more accessible, and relevant.

I see the extragalactic scene as more of an academic exercise, whereas the situation within our own galaxy is of immediate import and interest as regards the history of our solar system--and other readily observed, nearby objects.


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Niels2011
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Re: Visualising large scale structure in the night sky new [Re: GlennLeDrew]
      #5881562 - 05/24/13 02:24 AM

I'll get my coat!

Seriously though, it is not an unreasonable topic but maybe there really is not much interest then fair enough. I can understand your point of view for yourself but of course I have mine and I do not think they are mutually exclusive - I also love observing the objects within our Galaxy. Where we differ is maybe that I am particularly interested in Galaxies and you perhaps not so much if I am understanding right. But I do feel on safe ground saying that there are lots of people on CN interested in observing Galaxies, so my interest in that is definitely shared. Then this further aspect of it caught my interest - maybe no-one else is interested, but if they are it would be very interesting to read a thread of posts of people's different points of view and experiences...

In the meantime, thank you for your replies, I'm enjoying the debate, although I really am interested in hearing from others who are maybe interested.

I also see you have a Mallincam - I think I was reading some of your contributions in another post on Mallincams, they sound like fantastic bits of kit and you must get very good views with it; I'm definitely tempted but it would take a bit of saving so it's out for now.

Clear skies to all,
Niels


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Niels2011
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Re: Visualising large scale structure in the night sky new [Re: Niels2011]
      #5881569 - 05/24/13 02:43 AM

So, hi, I'm quite new to posting here, anyone else interested inthis topic, it would be very interesting to read anyone's thoughts and experiences.

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WeltevredenKaroo
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Re: Visualising large scale structure in the night sky new [Re: Niels2011]
      #5881637 - 05/24/13 05:38 AM

I sense there are many discoveries, and joys, to be had at any level of our study. Like Glenn, I am most fascinated by the magnitude and minutia of our host galaxy. I could say the same were I to zero in on the Carina Nebular Region, the Local Group, the solar system, the Moon. No matter the distance, there something to learn, teach, and enjoy. And instrumentation or personal budget need not limit our horizons, either. I'm limited to 200mm on an alt-az. Yet recently I tracked down several PGCs in Abell 1367 in Norma. Three faint fuzzies, ephemeral yet there. There are the most visible in the Norma Cluster. Research in to that led me to the Great Attactor, the ten years of investigation that finally charted the Galactic Superplane, Shapley Supercluster, and immense filament on all which all these lie. Yet even that was not the end of the fun. I came across a recent paper by Beygu, Krekel et al in the Netherlands, which identifies a 3-galaxy group designated VGS-31 (Markarian 1477 & Arekelian 409) that has evolved from the influence of dark, not baryonic, matter. It formed in one of the galactic voids completely isolated from the type of filaments on which the bulk of galactic clusters lie. [see: http://arxiv.org/pdf/1303.0538v1.pdf] These three galaxies, the Begyu paper asserts, evidence properties unlike other galaxies. I felt a sense of what Tycho Brahe may have felt when he looked up from his armillaries nd sextants at the apertures in the roof of his half-subterranean observatory, and said to himself, 'Beyond these apertures are matters I shall never see, but know are there.'

So where in all the above is our Milky Way? What's the connection?

The Norma Cluster, Great Attractor, and a dozen other clusters from Antlia through Pavo pass through the Zone of Avoidance, our own Galaxy's disc of dust and gas. Our Galaxy's extinction zones mimic supergalactic filaments in their intricacy and gravitationally-driven properties. Starting with Shlegel et al in 1998, the darkness in our galaxy has been mapped till it's as lucid as light. I can see these very same obscuring filaments in a Norma eyepiece field as intricately woven as star lanes in a great globular. There is as much to learn, and again, in which to take joy, in the darkness as there is in the light. Those dark threads of dust in our very own spiral arm, are Tycho Brahe holes in the roof, beyond which great wonder lies.


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Tom Polakis
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Re: Visualising large scale structure in the night sky new [Re: Niels2011]
      #5881918 - 05/24/13 10:15 AM

Thanks, Neils. What a great Web site! I will look at anything from the moon through quasars, but there aren't many subjects that interest me more than large-scale structure of the universe. My eye-opening moment in this subject came about when I was observing the Local Group in 1990, and as part of my library work, discovered Tully's Nearby Galaxies Atlas. It contains unique 2-D representations of the 3-D structure, plotted in an atlas that's similar in size and format to Tirion's Sky Atlas 2000.0.

When I'm looking at galaxies through the eyepiece, I am constantly trying to get my arms around their relative distances. While none of us can relate to these distances, we can comprehend them.

Tom


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Sarkikos
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Re: Visualising large scale structure in the night sky new [Re: GlennLeDrew]
      #5882261 - 05/24/13 01:02 PM

Glenn,

Quote:

Within our own Galaxy, where, moreover, small instruments can be brought to bear, we observe a *very* much wider array of objects in close proximity which interact on vastly smaller time scales. Much more accessible, and relevant.

I see the extragalactic scene as more of an academic exercise, whereas the situation within our own galaxy is of immediate import and interest as regards the history of our solar system--and other readily observed, nearby objects.




I share this view, also. But even for our own galaxy, it can be challenging to built up even the simplest internal 3D map. After all, when we look at the night sky, we see an apparent 2D hemisphere, not three dimensional space. Besides, with the real threat of dumbing-down the hobby through goto and DSCs - yes, I said it! - probably many observers don't even have a very good idea of where objects are located in a two-dimensional sense. The only location some are concerned about is "in the eyepiece."


Mike


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GlennLeDrew
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Re: Visualising large scale structure in the night sky new [Re: Sarkikos]
      #5882510 - 05/24/13 03:04 PM

Niels,
I wasn't trying to start a 'debate.' But I guess I did, in a way. Some years back I purchased Tully's galaxy atlas. After many, many hours of bending my mind over the various 2-D and 3-D charts, I still found it not so easy to retain a coherent picture. And I suppose it was just a lack of fascination which kept me from persevering. But I did try! At least I have a picture built up of our own Local Group of galaxies...


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GlennLeDrew
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Re: Visualising large scale structure in the night sky new [Re: GlennLeDrew]
      #5882522 - 05/24/13 03:14 PM

I must mention a neat, free, software package which should fill the bill for both our home galaxy and the larger universe of galaxies...

Partiview, from the Hayden Planetarium. You can get either or both of a set of databases, for the Milky Way and for external galaxies. It's OpenGL-based, and so looks very nice. And it doesn't generate a Windows registry entry, meaning you can simply drop it anywhere in your machine.

Incidentally, I supplied the OB association database, after noting this lack when I first tried the package in 2003. Which illustrates the fact that the user can fashion any database imagined...


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Niels2011
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Re: Visualising large scale structure in the night sky new [Re: GlennLeDrew]
      #5882742 - 05/24/13 05:23 PM

Quote:

Niels,
I wasn't trying to start a 'debate.' But I guess I did, in a way. Some years back I purchased Tully's galaxy atlas. After many, many hours of bending my mind over the various 2-D and 3-D charts, I still found it not so easy to retain a coherent picture. And I suppose it was just a lack of fascination which kept me from persevering. But I did try! At least I have a picture built up of our own Local Group of galaxies...




Thanks Glenn, I think I'm just at that stage, trying to form a mental picture. A couple of mentions of the Tully atlas here, which I'm going to check out. I'm just remembering years ago, before I had a scope, I had an edition of starry night which allowed you to 'fly' around it in a virtual spaceship
Niels


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Niels2011
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Reged: 06/09/11

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Re: Visualising large scale structure in the night sky new [Re: GlennLeDrew]
      #5882752 - 05/24/13 05:27 PM

Quote:

I must mention a neat, free, software package which should fill the bill for both our home galaxy and the larger universe of galaxies...

Partiview, from the Hayden Planetarium. You can get either or both of a set of databases, for the Milky Way and for external galaxies. It's OpenGL-based, and so looks very nice. And it doesn't generate a Windows registry entry, meaning you can simply drop it anywhere in your machine.

Incidentally, I supplied the OB association database, after noting this lack when I first tried the package in 2003. Which illustrates the fact that the user can fashion any database imagined...




Thanks for this also, that looks very interesting,
Niels


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Niels2011
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Re: Visualising large scale structure in the night sky new [Re: WeltevredenKaroo]
      #5882805 - 05/24/13 05:56 PM

Quote:

I sense there are many discoveries, and joys, to be had at any level of our study. Like Glenn, I am most fascinated by the magnitude and minutia of our host galaxy. I could say the same were I to zero in on the Carina Nebular Region, the Local Group, the solar system, the Moon. No matter the distance, there something to learn, teach, and enjoy. And instrumentation or personal budget need not limit our horizons, either. I'm limited to 200mm on an alt-az. Yet recently I tracked down several PGCs in Abell 1367 in Norma. Three faint fuzzies, ephemeral yet there. There are the most visible in the Norma Cluster. Research in to that led me to the Great Attactor, the ten years of investigation that finally charted the Galactic Superplane, Shapley Supercluster, and immense filament on all which all these lie. Yet even that was not the end of the fun. I came across a recent paper by Beygu, Krekel et al in the Netherlands, which identifies a 3-galaxy group designated VGS-31 (Markarian 1477 & Arekelian 409) that has evolved from the influence of dark, not baryonic, matter. It formed in one of the galactic voids completely isolated from the type of filaments on which the bulk of galactic clusters lie. [see: ]http://arxiv.org/pdf/1303.0538v1.pdf] These three galaxies, the Begyu paper asserts, evidence properties unlike other galaxies. I felt a sense of what Tycho Brahe may have felt when he looked up from his armillaries nd sextants at the apertures in the roof of his half-subterranean observatory, and said to himself, 'Beyond these apertures are matters I shall never see, but know are there.'

So where in all the above is our Milky Way? What's the connection?

The Norma Cluster, Great Attractor, and a dozen other clusters from Antlia through Pavo pass through the Zone of Avoidance, our own Galaxy's disc of dust and gas. Our Galaxy's extinction zones mimic supergalactic filaments in their intricacy and gravitationally-driven properties. Starting with Shlegel et al in 1998, the darkness in our galaxy has been mapped till it's as lucid as light. I can see these very same obscuring filaments in a Norma eyepiece field as intricately woven as star lanes in a great globular. There is as much to learn, and again, in which to take joy, in the darkness as there is in the light. Those dark threads of dust in our very own spiral arm, are Tycho Brahe holes in the roof, beyond which great wonder lies.




Thank you WeltevredenKaroo, what a lovely post. I had a look at the VGS-31 paper, very interesting; on the sky it's just south of M63 I see, though it must be a way further away, I haven't managed to find the distance or redshift yet. I'm really looking forward to exploring all these structures intra or extragalactic; and especially an observing project of large scale structure is beginning to take form in my mind - and also Glenn's post is making me think of trying to get impressions of galactic structure too.
Bw
Niels


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Niels2011
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Re: Visualising large scale structure in the night sky new [Re: Tom Polakis]
      #5882834 - 05/24/13 06:22 PM

Quote:

Thanks, Neils. What a great Web site! I will look at anything from the moon through quasars, but there aren't many subjects that interest me more than large-scale structure of the universe. My eye-opening moment in this subject came about when I was observing the Local Group in 1990, and as part of my library work, discovered Tully's Nearby Galaxies Atlas. It contains unique 2-D representations of the 3-D structure, plotted in an atlas that's similar in size and format to Tirion's Sky Atlas 2000.0.

When I'm looking at galaxies through the eyepiece, I am constantly trying to get my arms around their relative distances. While none of us can relate to these distances, we can comprehend them.

Tom




Hi Tom, I'm with you there - I also just enjoy viewing about anything, mostly moon and Saturn in the last few days, but I find galaxies and the large scale structure perhaps most fascinating of all. I'm finding all of these suggestions very helpful, and I want to take a proper look at the Tully database too. Thanks for that.

I was plotting distances of the galaxies I recently observed on my sky atlas 2000.0 and beginning to see relationships between them which are quite different from their place on the sky. For instance in the same region of sky, NGCs 4214, 4244 and 4151 are 10 to 14 Mly distant, and close by 4145 and 4369 are 40 and 44 Mly away and more closely related to eachother, though 4145 and 4151 appear practically next to eachother in the sky - I'm enjoying this extra sense of interrelation in retrospect, but I will very likely make it part of my planning too so I can appreciate it at the eyepiece.


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Sarkikos
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Re: Visualising large scale structure in the night sky new [Re: Niels2011]
      #5883073 - 05/24/13 08:35 PM

Has anyone tried this program?

Where is M13?

It looks like a much simpler way to get a good overview - literally and figuratively - of the structure of our galaxy without an overabundance of intervening verbiage or math. I think a visually-based understanding is probably best for most humans.

Mike


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Niels2011
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Re: Visualising large scale structure in the night sky new [Re: Sarkikos]
      #5883453 - 05/25/13 03:30 AM

Quote:

Has anyone tried this program?

Where is M13?

It looks like a much simpler way to get a good overview - literally and figuratively - of the structure of our galaxy without an overabundance of intervening verbiage or math. I think a visually-based understanding is probably best for most humans.

Mike




Dear Mike, thanks, that looks great!

Niels


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Sarkikos
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Re: Visualising large scale structure in the night sky new [Re: Niels2011]
      #5883821 - 05/25/13 11:32 AM

Where is M13? has filters for the Messiers, some NGC objects, Collinder, Caldwell, as well as Bayer and Flamsteed stars. So the program can help the user visualize locations of objects - other galaxies - outside our galaxy, also.

Mike


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Niels2011
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Re: Visualising large scale structure in the night sky new [Re: Sarkikos]
      #5884393 - 05/25/13 05:29 PM

Yes, this looks really good all round for the job of visualising 3D relations of objects inside and outside the galaxy. I'm away from my PC for a few days, so I'm going to have to wait to try it out - great stuff.
Bw
Niels


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WeltevredenKaroo
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Re: Visualising large scale structure in the night sky [Re: Niels2011]
      #5884538 - 05/25/13 07:00 PM

Niels, here's a couple of other visual aids:

http://www.atlasoftheuniverse.com/

And this one must have taken a considerable mount of graphic skills and hours of time:

http://www.newgrounds.com/portal/view/525347


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