A brief diversion for astronomers

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Sableagle
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A brief diversion for astronomers

Postby Sableagle » Fri Aug 31, 2018 10:34 am UTC

Figure out how old the globe is!

P8131378 Rundale Palace sky globe.png


I suppose astrologers could try too but may find the implications disturbing.
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Re: A brief diversion for astronomers

Postby ThirdParty » Wed Sep 05, 2018 3:49 am UTC

I don't know much about astronomy, but decided to give it a try anyway.

The stars seem to be about 2.5° to 3° off from the coordinates they had in 2000. (For example, I think the bright star at 17° on the ecliptic is Zeta Piscium, whose celestial longitude in 2000 was about 19.9°.) Since it takes about 26000 years to precess 360°, that means that the globe is portraying a date around 1780-1820.

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Re: A brief diversion for astronomers

Postby Eebster the Great » Thu Sep 06, 2018 8:28 am UTC

Interesting that it has both French and Latin. It looks very well crafted for the time, which I would guess is 18th century. I don't know what it is about Andromeda, but somehow her line drawing looks French to me too.

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Re: A brief diversion for astronomers

Postby ThirdParty » Thu Sep 06, 2018 1:40 pm UTC

I agree that it's French in both language and appearance. The illustration seems reminiscent of (but not identical to) the star maps created by Ignace-Gaston Pardies in the late 17th century.

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Re: A brief diversion for astronomers

Postby p1t1o » Thu Sep 20, 2018 11:06 am UTC

ThirdParty wrote:I don't know much about astronomy, but decided to give it a try anyway.

The stars seem to be about 2.5° to 3° off from the coordinates they had in 2000. (For example, I think the bright star at 17° on the ecliptic is Zeta Piscium, whose celestial longitude in 2000 was about 19.9°.) Since it takes about 26000 years to precess 360°, that means that the globe is portraying a date around 1780-1820.


Might it be worth noting that the Greenwich meridian was adopted as the prime meridian in 1884, and the paris meridian (which would have been popular on french cartography before this) was about 2 degrees east of the greenwich meridian?

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Re: A brief diversion for astronomers

Postby gmalivuk » Thu Sep 20, 2018 11:33 am UTC

Earth's longitude is irrelevant for star maps. Things are measured from the equinox point.
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Re: A brief diversion for astronomers

Postby ThirdParty » Fri Sep 21, 2018 1:42 am UTC

p1t1o wrote:Might it be worth noting that the Greenwich meridian was adopted as the prime meridian in 1884, and the paris meridian (which would have been popular on french cartography before this) was about 2 degrees east of the greenwich meridian?
The line I'm taking for 0° is labeled "Colure des Equinoxes". I don't speak French, but I think it's safe to translate that to "Equinoctial Colure".

And although the numbering on the ecliptic is a little bit unclear, the fact that the numbering on the equator says "10" in one direction and "350" in the other makes me reasonably confident that the red and white stripes each represent 1°.

So I don't think I have the wrong coordinate system.

(I'm more worried about whether I've done the math correctly. Wikipedia gives star coordinates in terms of right ascension--measured in hours--and declination, whereas I'm estimating Zeta Piscium's coordinates on the globe in terms of ecliptic longitude--measured in degrees. The globe is inverted relative to the sky. And I really don't know anything about astronomy. So someone should double-check my calculation.)


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