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General Astronomy >> General Observing and Astronomy

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drollere
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Reged: 02/02/10

Loc: sebastopol, california
Re: unlearning the constellations new [Re: CounterWeight]
      #5514487 - 11/11/12 01:29 PM

Quote:

As I tried to link to... a 3D representaion has ALREADY BEEN DONE. Please convince me you are not re-inventing the wheel. What are you bringing to the party that others have not already contributed?



i've been as plain as i know how to be: the goal is to identify naked eye markers and asterisms, easily identified in the night sky and easily remembered as indicators of basic facts, facts that represent a basic orientation to our place in the galactic landscape and identify features that are significant examples of galactic process.

i believe i have never challenged the utility of the IAU constellations as tracts in a "two dimensional" celestial area, and i have never made the claim that the past needs to be discarded as useless.

yes, i have said that the tracts are inherently arbitrary, and that the past is fine for those who find it interesting, and specifically that cultural history is irrelevant to organizing and remembering our current understanding of the galaxy.

and yes, i have made the claim that the currently available astronomical literature offers very little support for anyone interested to "see" the galactic landscape apparent to us, and i have made the claim that it is useful to "forget" or "unlearn" the constellations in order to let the eyes (not the learned constellation concepts) do the looking in order to find and piece together the useful asterisms and markers. (see the post above about how the constellations actually appear to the naked eye, if viewed without prejudice as to "what i should see".)

what part of that is unclear or poorly expressed?

Quote:

who's galactic landscape? What we do know of and have data for... already done, or am I missing something here? I and at least one other responder linked you to it. This for folks that have no access to the web or star chats/atlas? Living in the city and can't see milky way? And it's to be somehow intuitive? All inclusive?



you're throwing a lot of issues at me there. but the nub is this: go to "atlas of the universe", or pick up henbest & couper's "guide to the galaxy", and you have a trove of catalog and graphic information about the galaxy, as imaged from a point far from the earth.

my question to you: what does all that look like as imaged from the earth? if you go out to the sky tonight, in which direction are the significant features?

it's an entirely different cognitive and spatial problem to orient yourself to a map of new york, to orient yourself while standing in times square, and to connect the two as an intuitive understanding of direction and distance. yes, there are lots of maps or three dimensional visualizations of the galaxy. but none of that is helpful to the naked eye or binocular astronomer as an answer to where we are located, what we can see from where we are located, and how what we can see relates to the whole.

that is explicitly stated in the OP: i said i was looking at the sky, and realized that the traditional constellations did not clearly or memorably indicate the major galactic features visible to me.

a simple example is that there is no asterism commonly used by astronomers to identify the center of the galaxy in the same way that there is an asterism (the dipper) commonly used by astronomers to find the pole star. or to identify the local arm. or to identify the galactic pole. and so on ...

in other words, there is no astronomical "lore" delving the galactic landscape as viewed from earth that even begins to rival (much less challenge) the lore about constellations -- their antiquity, their mythology, and their shopping basket contents of interesting and conceptually unrelated things to look at within an arbitrary area of sky.


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bumm
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Re: unlearning the constellations new [Re: drollere]
      #5514513 - 11/11/12 01:50 PM

Drollere was saying

a simple place to start the list of anchor or critical stars, the bright stars that orient the observer to the galactic landscape, is with local bright stars -- "companion" stars.

But how do we find these more suitable anchor stars? By their position in the constellations?
Marty


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drollere
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Re: unlearning the constellations new [Re: drollere]
      #5514573 - 11/11/12 02:26 PM

we have the companion stars, we know that rigil kent, sirius, procyon, altair, vega, fomalhaut and (approximately) arcturus are all within 10 parsecs. and these bright stars define an area of many unseen companion stars, but most too numerous and faint to identify.

the first asterism is the "summer triangle" of altair, vega and deneb. this is my first galactic asterism.

the elegance of this asterism is that it actually defines a long rectangle receeding into the distance, like a long, straight, road. to anchor the point, i can draw it with a dotted line down the middle:

we have the companion stars, we know that rigil kent, sirius, procyon, altair, vega, fomalhaut and (approximately) arcturus are all within 10 parsecs. and these bright stars define an area of many unseen companion stars, but most too numerous and faint to identify.

the first asterism is the "summer triangle" of altair, vega and deneb. this is my first galactic asterism.

the insight provided by this asterism is that it actually defines a long rectangle receding into the distance, like a long, straight, road. to anchor the point, i can draw it with a dotted line down the middle:



vega and altair, as companion stars, are both quite close to us (about 6.5 parsecs) and to each other (about 4.5 parsecs). in contrast, deneb is very far away -- so far away that its distance is uncertain. i've put it at 990 parsecs, but 1000 parsecs is easy to remember and 100 times farther than our companion stars, if we just say they are 10 parsecs distant and 5 parsecs apart.

now, simple perspective means deneb is the vanishing point, so that the width of the two sides of the triangle common to deneb defines the visual distance between altair and vega at greater distances than 10 parsecs. and this is measured as the distance from deneb to the baseline between vega and altair -- geometrically, the triangle height. located at half height from deneb, the baseline is twice the baseline distance of 10 parsecs, or 20 parsecs away; at 1/4 height, it is 40 parsecs; at 1/10 height, it is 100 parsecs, and so on. the triangle becomes a simple visual guide to judging the effects of distance on apparent size.

the three crossarm stars in cygnus, indicated by their bayer letters, can be distance located along this "road". the location of the 4.5 parsec baseline is shown for delta and epsilon, which are roughly 3 times and 8 times farther from us. the baseline for gamma is not shown because it is half the distance between us and deneb, or 470 parsecs, so its perspective baseline would be located 10/500 the triangle height from deneb.

it's possible to lard this framework with a lot more spatial information, for example as the apparent separation of the 5 parsec interval at different distances, or the apparent magnitude of vega and altair at those distances:



so this asterism -- the summer triangle with the three crossarm stars, forms a visually obvious and intuitive illustration of distance and the effects of distance on visual size and magnitude.

the fact that vega and altair at the distance of del Cyg are both near the naked eye threshold, and at gam Cyg are far below that threshold, gives some context to what distance means to "solar type" magnitudes (both are type A stars, roughly 30 times brighter than the sun). using the inverse square law, we know that vega and altair at twice their distance (near epsilon) will appear 1/4 as bright, and at the distance of deneb will appear 1/10,000th as bright.

the fact that at deneb's distance they would appear separated by only 16 arcminutes puts context around distance and apparent size.

there is also the fact that the vega altair baseline cuts across the visible galaxy at about galactic longitude 60º, which has been found by radio astronomy to be the "tangent line" or outer border of the galactic arm nearest to us toward the galactic nucleus (the carina sagittarius arm, which as we now see extends far beyond sagittarius). so this triangle actually forms a "window" through which we see the interval between this inner arm and our local arm -- we are looking between the two arms, as if looking up a long canyon or valley ... or the way a surfer, riding a large wave, looks back at the curl closing behind him.

it also reveals a significant problem: accuracy is a form of clutter. not a lot is lost by saying deneb is 1000 parsecs rather than 990 parsecs distant. or that vega and altair are separated by 5 parsecs rather than 4.5 parsecs, or that epsilon is 20 rather than 22 parsecs and delta 50 rather than 52 parsecs and gamma 500 rather than 470 parsecs away. the simpler numbers are easier to remember, and easier to manipulate as ratios of triangle height (1/2, 1/5, 1/50).

explaining the galactic landscape to a novice or a young person, simplification is essential. it's only by looking at several galactic asterisms that we can decide how much simplification is necessary as a general principle.


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CounterWeight
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Re: unlearning the constellations new [Re: drollere]
      #5515584 - 11/12/12 07:57 AM

Not trying to disagree with anything, but am curious if you have read that book "A Skywatchers Year" by Jeff Kanipe? I was looking through for candidate stars and reference... just curious.

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drollere
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Reged: 02/02/10

Loc: sebastopol, california
Re: unlearning the constellations new [Re: bumm]
      #5517714 - 11/13/12 11:23 AM

Quote:

But how do we find these more suitable anchor stars? By their position in the constellations?



all i can say is, try the "naive looking" i described in a post above.

i'm pretty sure that you do not locate the constellation canis major in order to find sirius, or piece together the faint stars of lyra to identify vega. you don't first find the constellation of canis minor in order to find procyon ... because procyon is all there is.

bright stars form a whole sky pattern, and that is how you orient to fainter patterns.

indeed, if you study the history of astronomy as crossen advocates, you'll find that bright stars (such as sirius) and a few bright asterisms (dipper, orion, pleiades) are at the root of sky lore. constellations as a general feature of astronomy appear with the rise of astrology, and with the need to identify fainter stars by their position within a standardized figure. this method is fully developed in ptolemy, and persists until william herschel.


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drollere
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Re: unlearning the constellations new [Re: drollere]
      #5517855 - 11/13/12 12:40 PM

looking outward from the galaxy center, the galaxy band presents a striking contrast from the summer triangle:

1. there are many more bright stars
2. the galaxy band appears less bright, or is not visible

the bright stars form an enormous and complex pattern, as illustrated below.



the important goals are, again, to anchor concepts of distance and scale, and to identify important features. i played around with different groupings, starting with the large hexagon formed by sirius, procyon, pollux, capella, aldebaran and rigel. but i ended up with something more modest: three triangles. i've also added star nomenclature, distances, spectral types and molecular cloud imagery.



1. the distance from pollux to capella is 34º, the same as the distance from vega to altair. it can be used in the same way to evaluate apparent size in relation to distance.

2. the triangle of alhena, capella and aldebaran is centered on alnath, and distances form a 10, 20, 30 and 40 parsec sequence, in alpha beta gamma order. the triangle encloses the auriga gap, and the gem OB1 molecular complex at 2000 parsecs distance.

3. a line extended from capella through alhena defines the north and east edge of the molecular concentrations, which are bounded on the south and west by a line from betelgeuse to sirius: the galactic equator is midway between them. the north line passes near the old and young clusters M46 and M47, at about 1700 and 500 parsecs distance, which therefore are situated above (direction of galactic north) the midplane of the galaxy disk.

4. the triangle of sirius, betelgeuse and rigel encloses the molecular clouds associated with barnard's loop and the orion nebula, a star forming region at around 400 parsecs distance.

5. the stars of the orion asterism are all closer to us than the nebula, by almost half. rigel, saiph and the outer belt stars from a trapezoid at about 250 parsecs; betelgeuse is at roughly half that (130 pc), and bellatrix at roughly half that again (75 pc).

6. the most distant bright star in this area is eta canis majoris, at 980 pc, almost exactly the same distance as deneb. as a visual cue of depth, the triangle of eta with wezen and adhara is, at its distance of ~1000 pc, the same size as the triangle of sirius, betelgeuse and rigel, visualized at rigel's distance of 250 pc. both triangles lie on the inner side of the local arm, and visually describe its recession away from us.

7. stars toward the orion asterism are relatively young and many are intrinsically bright. in fact, they form an orderly sequence in which the absolute magnitude increases with distance: this is why all stars in the asterism are comparably bright.



the sirius triangle region is an excellent illustration of molecular clouds, H-II regions and massive star formation, absolute magnitude and distance, and a good range of "early" or recently formed spectral types.

despite the numerous bright stars, this whole area is relatively barren of distant structures. a "perseus arm" is hypothesized to lie at a distance of 2000 to 3000 parsecs, but the arm is not clearly defined and in fact a considerable extent of the galaxy outward from the sun's location appears turbulent and disrupted. the conventional image of the galaxy is misleading when it shows dense, clearly defined spiral arms in this direction.


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drollere
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Reged: 02/02/10

Loc: sebastopol, california
Re: unlearning the constellations new [Re: CounterWeight]
      #5517869 - 11/13/12 12:47 PM

Quote:

am curious if you have read that book "A Skywatchers Year" by Jeff Kanipe? I was looking through for candidate stars and reference... just curious.



don't know it, but i will look for it. thanks!

i am leaving today to boot up a house in mariposa, california, the possible site of future observing. i'll return to this topic later this week.


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CounterWeight
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Re: unlearning the constellations new [Re: drollere]
      #5519588 - 11/14/12 02:09 PM

Bruce,

Nice work there!

I think it's still available("A Skywatchers Year" by Jeff Kanipe), but a bit pricy, i think my version is from 1999 - maybe better to find at a used book store if one in your area.

it's a very diferent treatment of the topic, though i think in ways very much along the lines of what you might be after, I am just saying 'along the lines'. it does include some very widefield orientation diagrams and amplifying info about galaxy disk and things like where a meteor shower will come from... it's really an educational read in ways others aren't, part of it by virtue of a weekly indexing.

One useful device I have is the Daivid Levy 16" planisphere. This planisphere includes outline of Milky Way (with center mark near Saggit/Scorp), Ecliptic path of planets, and interestingly the triangle formed by Altair, Deneb, Vega that contains the 4 star structure of Cygnus. Being large it is far easier to use at night than my small ones.

It's impressive how much it can convery in a very short amount of time. yet by virtue of that can also come up quite short without a lot of amplifying information, depending.

I'm not trying to be contrarywise to what you are after at all. Just the curse of being a bookworm is I have many books and more than a few planishpheres.

That's why I am putting all the Q's out to about the idea. Rare ocassions where my daughter has friends over and it's clear and I'm doing visual, I love to hand them the planisphere and show it's usefulness as an orientation tool, then if attention span still there show the 'books'. But for all that, still extremely difficult to convey as you mention our 'neighborhood' and then even more the relationship of this neighborhood to the rest. Of all questions the 'how far away' is most asked. If I'm understanding your intentions there is definately room for something that could easily and quickly convey this, and I suspect it would be quite popular


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bumm
sage


Reged: 01/07/11

Loc: Iowa
Re: unlearning the constellations new [Re: drollere]
      #5519901 - 11/14/12 06:19 PM

Quote:

Quote:

But how do we find these more suitable anchor stars? By their position in the constellations?



all i can say is, try the "naive looking" i described in a post above.

i'm pretty sure that you do not locate the constellation canis major in order to find sirius, or piece together the faint stars of lyra to identify vega. you don't first find the constellation of canis minor in order to find procyon ... because procyon is all there is.

bright stars form a whole sky pattern, and that is how you orient to fainter patterns.

indeed, if you study the history of astronomy as crossen advocates, you'll find that bright stars (such as sirius) and a few bright asterisms (dipper, orion, pleiades) are at the root of sky lore. constellations as a general feature of astronomy appear with the rise of astrology, and with the need to identify fainter stars by their position within a standardized figure. this method is fully developed in ptolemy, and persists until william herschel.




Well, I can't speak for everyone, but I pretty much see the sky as a whole. Often, a bright star in a known location IS easier to pick out than the surrounding constellation. However, I generally confirm the identity of a star by looking at it's position among it's fellows... i.e. the constellations. This is true especially if I happen to be out at an unusual time. The Summer triangle is very conspicuous, and it's easy to identify the individual stars. However, it's not worth much for starhopping. I see Canis Minor as two stars... the brighter one is Procyon. By itself, theres nothing distinctive about Procyon. I'd have to confirm it's identity by the way it relates to Gemini. Sirius isn't much of a problem that way... it's distinctly BRIGHT. However, how many of us don't notice that it's following Orion?
Planispheres have been brought up in this discussion. I happen to collect old planispheres and love the things. (as some here might guess. ) However, when I look at a military type planisphere showing only navigational stars with no constellations, I can eventually get oriented, but for my needs as an amateur astronomer, something is lost.
Not meaning to pick nits... You've put forth a considerable effort here. But still, I'm having trouble seeing the advantage of ignoring the constellations in favor of certain well picked individual stars.
Marty


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bryguy27007
super member
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Reged: 03/09/09

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Re: unlearning the constellations new [Re: Astrodj]
      #5533174 - 11/22/12 12:03 AM

Quote:

Bruce,

I imagine a planetarium program that could be told to show the naked eye sky from any location in or near the galaxy. It would be like having a virtual spaceship. One would quickly get lost if the program were so sophisticated as to able to put the reference point into light years per second motion.

I wouldn't mind heading out toward the Cone Nebula and tooling around for a while to see what the area looks like from other angles.

My interest in forming a mental picture of the actual 3D location of common celestial objects within our galaxy took
flight when I learned that the vast majority of what is visible to the naked eye is contained within a relatively small bubble of space with a radius of roughly 1500 parsecs, with us being in the center of the bubble.

Only 7,000 or so of the nearest AND brightest stars are visble to the unaided eye, mostly within that bubble, out of 2 or 3 hundred billion stars in the galaxy. Over half of either total are red dwarfs with only a scant few visible without optical aid, even the relatively near ones.

Looking toward the learned constellation of Saggitarius without optical aid, we can see (with a few exceptions) only about an eighth of the distance to the center of our galaxy. Same story along the galactic plane in the opposite direction towards the outer edge. Then there is the other entire half of the galaxy left to consider.

It's a lot to map, and I have only a very rudimentary knowledge of where the objects I can see actually are on that map so far, but I'm learning.

I too spend most of my time observing the "objects" in a telescope, because I enjoy it so much. But, I do make an effort to mentally place said object within our galaxy where it belongs, as best I can. Knowing what else is also in the locale of that object however, is another question that goes largely unanswered for me most of the time.




You might find this video extremely interesting.
http://www.youtube.com/watch?v=8agz9FcDcPk


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mark8888
Carpal Tunnel


Reged: 09/24/10

Re: unlearning the constellations [Re: bryguy27007]
      #5533664 - 11/22/12 10:12 AM Attachment (14 downloads)

http://workshop.chromeexperiments.com/stars/

Helloooooooooo easy to use 3D map. This is great.
The trick is to zoom out a little past the oort cloud and then get a sense of the layout and the grid pattern by moving the mouse and shifting your perspective. Then zooming out slightly more and doing the same. Takes a little while to get the hang of it but the effort is rewarded. Awesome!
Works in chrome and possibly firefox, but apparently not explorer.
No program to download or instruction book to read. It works right in the browser.
By the way, of course I didnt make this! Others have been linking to it.
I'll attach a screen shot of this program in action.


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dUbeni
member


Reged: 04/12/10

Loc: Lisboa, Portugal
Re: unlearning the constellations new [Re: Dennis_S253]
      #5541310 - 11/26/12 11:27 PM

Thank you OP, and all those that contributed to this "Great Post". A true insight into our home in the Milky-Way galaxy.

Quote:

... The thing that makes me wonder is "how" did the old ones get all there idea's? They didn't have light pollution, I don't think. And as some have said, from a dark sky there are so many stars that it is hard to pick out constellations. Orion is just a bunch of stars. Bright stars that make a pattern that is one of the most reconized. I'm sure that (I know) all them stars are not all associated with each other.




They didn't have light pollution but they had the moon, and in a moonlit night, even with great skies, only some asterism standout. To them stars were fixed on a sphere,there were no distances, and maybe they just named the asterisms after things that were significant to there life's, like the hunter, the water bearer, the bull, the ram, etc.
Until recently the only asterism I knew was a trapeze with 3 stars on a diagonal that I called "the 3 Mary's", now I know it's part of the Orion constellation. When I was 12 years old, and men went to the moon, I started wondering about the universe and how it would be like to see it from the outside, and how far out would I have to go, knowing it was impossible due to its infinite size.

As a beginner (2007), I obviously started with the constellations, as a road map of the sky in medium polluted skies, it works well. Anyway I feel the need know more about the relative position of the solar system plane and the galactic plane and how objects fill the space around us.
I support the idea of OP, of creating new maps of the sky with more 3D and galactic information.
It is fun to look at distribution of open clusters along the galactic plane vs the globular clusters on Hayden Digital Universe. Although I new that, its hard to see it on the charts.
I'm having a lot fun with the Hayden Digital Universe, great perspectives from within and the outside Milky-way (just starting to use it).

Clear skies
Bernardo


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Starman1
Vendor (EyepiecesEtc.com)
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Reged: 06/24/03

Loc: Los Angeles
Re: unlearning the constellations new [Re: dUbeni]
      #5542370 - 11/27/12 03:52 PM

Periodically, the "veil lifts" and we see reality for what it is:
One night at Mauna Kea, observing with friends, the Milky Way rose.
Now, at that latitude, the Milky Way doesn't rise tipped to the horizon--it rises parallel to the horizon.
The bulge of the Milky Way made it look, and just for a while, as if I was IN a spiral galaxy, fairly near the core, and seeing the huge bulge of that core covering a good swath of sky in front of me.
At that moment, I actually 'felt" the size of the galaxy and our place in it. And, looking around at other areas of the sky, got a sense of three-dimensionality to the whole sky and all the stars seen.
These moments of personal serendipity are just too rare.


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payner
scholastic sledgehammer
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Reged: 03/22/07

Loc: Bluegrass Region, Kentucky
Re: unlearning the constellations new [Re: Starman1]
      #5542498 - 11/27/12 05:13 PM

Enjoyed reading your experienced perspective, Don. You drew an incredible picture with words.

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NGC7088
member


Reged: 12/31/12

Re: unlearning the constellations new [Re: payner]
      #5600556 - 01/01/13 11:52 PM

WOW!
What an amazing topic!
I started my "feel" for the galaxy by reading Crossen's Binocular Astronomy (first edition) way back when. To me he's the father of this topic and I feel honored and privileged to find he's still around and now I'm sharing not only an era but also web space with him. Hello Mr. Crossen, I don't even feel worthy to be here while you are!
To Drollere:
Write your book and all of us will read it and enjoy it and learn from it and be a bit wiser. But I guarantee you one thing. All your Group names and locations, associations and directions for "this and that" feature here and there will always contain reference to the ol' constellations names. Exactly like you've already done in each of your posts so far so it will be in your book. Because they are here to stay. Good luck!


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