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Celestial spheres with view from Earth?

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8 replies to this topic

#1 randallpatrickc

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Posted 20 November 2023 - 04:12 PM

I would really like one of these transparent celestial sphere models that show the sky as you would be looking up from earth in the middle. The only one that I have seen so far seems to have it printed like a regular star chart as if you were looking from outside the universe.

 

Anyone seen one printed the right way around, as if you are looking up as opposed to in? (You’d have to look through the sphere, past the Eath and onto the inside of the sphere).

 

The one that arrived today has it’s Earth come unglued and the wrong (to me anyway) way of printing the stars (or am I wrong?)

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Edited by randallpatrickc, 20 November 2023 - 06:27 PM.

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#2 rjacks

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Posted 21 November 2023 - 03:58 PM

The only way to make what you want is to create a human-size hamster ball with the night sky on the inside of the ball and you would stand/sit inside to look at it (i.e. a small planetarium). It would also need a system to orient you based on your latitude, date, and time.


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#3 brentwood

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Posted 21 November 2023 - 09:40 PM

I cannot make out how the stars are shown on this globe.  I looked into this a few years ago when I noticed  that the star map on a very expensive  globe was 'backwards'.  I wrote to the company but they did not know what I meant! I don't know why a star globe cannot be made with Sirius to the LEFT of Orion!  I don't know why you would need it to be transparent though.!


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#4 Jehujones

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Posted 21 November 2023 - 09:54 PM

I cannot make out how the stars are shown on this globe.  I looked into this a few years ago when I noticed  that the star map on a very expensive  globe was 'backwards'.  I wrote to the company but they did not know what I meant! I don't know why a star globe cannot be made with Sirius to the LEFT of Orion!  I don't know why you would need it to be transparent though.!

I agree, if you want the stars printed like the visible sky then there’s no reason to have it transparent and no reason to have earth inside.



#5 brentwood

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Posted 22 November 2023 - 01:22 AM

I agree, if you want the stars printed like the visible sky then there’s no reason to have it transparent and no reason to have earth inside.

It's weird though they make them ALL with stars backwards!  When I questioned them they said that they got the information from a reliable source !  Well I guess their globes would be accurate if they WERE transparent and you could get your head inside it!  Well I don't believe it. I went to do a search on what they all looked like when I wrote to the manufacturer , but now they are all corrected!  Did my letter actually make a difference? No way! grin.gif



#6 JohnTMN

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Posted 22 November 2023 - 01:38 AM

I would really like one of these,

Oh my gosh, I haven't seen one of those since Mr. Lemke's science class in 8th grade!
And that was 1972.

Good luck friend,


Edited by JohnTMN, 22 November 2023 - 01:39 AM.


#7 Tony Flanders

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Posted 22 November 2023 - 07:29 AM

I cannot make out how the stars are shown on this globe.  I looked into this a few years ago when I noticed  that the star map on a very expensive  globe was 'backwards'.  I wrote to the company but they did not know what I meant! I don't know why a star globe cannot be made with Sirius to the LEFT of Orion!  I don't know why you would need it to be transparent though.!

The Sky & Telescope star globe -- a true masterpiece -- shows stars in the same parity that you do when looking at the night sky. In other words, Sirius is to the lower left of Orion when you hold the globe with Polaris at the top. If you take any small rectangular slice of the globe and magnify it, it looks much like the charts in a conventional atlas.

 

I would be hard-pressed to say whether that's "frontward" or "backward." When you hold a celestial globe in your hands you're taking the "God's eye" view -- looking at the universe from the outside. Viewed that way, the S&T globe is in fact backwards. God would see Sirius to the lower right of Orion when Polaris is at the top.

 

Roger Sinnott told me that he did in fact consider producing a God's-eye celestial globe, but couldn't see what purpose it would serve, since no matter how you oriented the globe, it would never match what you actually see looking up from Earth's surface.

 

If you want a God's-eye globe to be useful, it does need to be transparent, because that way you can see the far side of the globe in "correct" parity, matching what you actually see when you look at the sky. But while that might be useful as a teaching tool, it's way easier to look at an opaque globe with the snail's-eye view. The S&T globe is in fact immensely useful if you want to find out what the sky looks like from alien latitudes.

 

When you view the far side of a transparent God's-eye globe, you're viewing the surface from the "wrong" side, which reverses the parity, just like looking in a mirror. That's an old trick for using conventional star charts with refractors. Look at the back of the chart, shine your flashlight on the front, and what comes through the paper will match what you see in the scope's eyepiece.

 

This is intimately related to the fact that on celestial charts east is to the left of north, whereas on terrestrial charts east is to the right of north, a fact that invariably confuses many newbies -- and continues to confuse me as well, even though I understand the reasons perfectly.



#8 Astrojensen

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Posted 22 November 2023 - 08:04 AM

It's weird though they make them ALL with stars backwards! 

No, it's not weird when you understand why. They are an accurate model of the sky, projected onto a globe. Since you can't look at it from the inside, the constellations appear mirror-reversed. A ray from the center of the globe, through any star on its surface, will project outwards and actually hit the real star, and vice versa. 

 

A globe, like the one from S&T, mentioned above, is actually mirror-reverse. You can't project a ray from the center and out through the stars on the globe, and hit the real star (okay, you can do it with one, but not two at the same time!). 

 

What is really sad is that no one understands celestial globes anymore and how useful they can be. A key component, missing from most of them, are the adjustable latitude, altitude (meridian) and azimuth (horizon) scale arcs. These turn a celestial globe into a sort of analog computer that can almost instantly calculate rise, transit and set times, as well as rise and set azimuths and transit altitudes. This was super useful in a time when such things were otherwise calculated with pen and paper.  

 

 

Clear skies!

Thomas, Denmark


Edited by Astrojensen, 22 November 2023 - 08:06 AM.


#9 StarBurger

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Posted 22 November 2023 - 08:17 AM

If you ever pass through Grand Central Terminal in NYC, check out the ceiling of the main concourse. It's the stars as if seen from the outside of a celestial globe.

Didn't need to be.

Also note that in one tiny corner there is a square patch of almost blackness remaining from the last cleaning to show how filthy the ceiling was originally.




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