Is there a standard mapping of celestial coordinates to geo-coordinates

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Discussion Overview

The discussion revolves around the mapping of celestial coordinates to geographic coordinates, specifically whether there is a standard correspondence between the two systems. Participants explore the implications of Earth's rotation and the potential for a fixed mapping that aligns celestial objects with specific locations on Earth.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant notes that celestial coordinates have a zero-point at the vernal equinox and questions if there is a standard mapping to Earth's surface.
  • Another participant explains that while the Earth is spinning, right ascension (RA) can correspond to longitude and declination to latitude, suggesting a projection of Earth's coordinates onto the sky.
  • A follow-up question seeks clarification on whether a fixed mapping exists that would allow constellations to consistently correspond to specific geographic locations.
  • One participant asserts that such a mapping has indeed been established as part of the celestial coordinate system's creation.
  • Further inquiries are made about the existence of a specific name for this mapping and resources to visualize it.
  • Suggestions are made to use planetarium software to visualize celestial coordinates based on user-defined geographic locations and times.

Areas of Agreement / Disagreement

Participants express varying levels of certainty regarding the existence of a standard mapping. While some assert that a correspondence exists, others seek more specific information and resources, indicating that the discussion remains somewhat unresolved.

Contextual Notes

Participants discuss the implications of Earth's rotation on the mapping of celestial coordinates, emphasizing that any correspondence can only be valid at a specific moment in time. There is also mention of the need for a fixed reference point, such as the vernal equinox, in establishing this mapping.

Who May Find This Useful

Individuals interested in astronomy, celestial navigation, or the relationship between celestial and geographic coordinates may find this discussion relevant.

Adam Laceky
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Sorry, I'm not an astronomer. This question relates to the book "S." by Doug Dorst.

I understand that the celestial coordinates have a zero-point at the vernal equinox. (0h, 0m, 0s RA, 0⁰, 0", 0' Dec.)

I also understand that it's possible to map these coordinates to spherical, or geo-coordinates.

My question: Is there a standard mapping of celestial coordinates to the surface of the Earth? I bet that if there is, the vernal equinox would be pinned to 0⁰ N, 0⁰W. (The equator at GMT.)

For instance, Sagittarius, which is at 19h, 0m, 0s RZ, -25⁰, 0", 0', would map to 75⁰ W, 25⁰ S.

Is there such a correspondence, or did I just make that up?
 
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Of course, the Earth is spinning, so any correspondence can only occur at an instant in time. But yes, if you convert RA into degrees then RA corresponds to longitude, and declination corresponds to latitude. This is basically where the celestial coordinates come from. You can think of them as taking the Earth longitude and latitude lines and projecting them onto the plane of the sky.
 
phyzguy said:
Of course, the Earth is spinning, so any correspondence can only occur at an instant in time. But yes, if you convert RA into degrees then RA corresponds to longitude, and declination corresponds to latitude. This is basically where the celestial coordinates come from. You can think of them as taking the Earth longitude and latitude lines and projecting them onto the plane of the sky.

I understand that the Earth is rotating. I'm asking if there's a standard, fixed mapping of celestial coordinates to the surface of the Earth. Say, 0⁰ N, 0⁰ W would correspond to the vernal equinox. So that any given constellation always corresponds to a location on Earth's surface.

Has this already been done?
 
Adam Laceky said:
Has this already been done?

Yes. As I said, this is how the celestial coordinate system was created.
 
Oh, OK. Thanks. Is there a name for this map? A Website I can go to and see the constellations mapped onto Earth?
 
Well, you could try overlaying these two. I think they are both Mollweide projections centered on (0,0)

Mollweide_Earth.png
Mollweide_Celestial.png
 

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There are also planetarium type programs that allow you to set your lat/lon to any value the time/date to any value and see what the sky looks like, including constellations. I use a free one called stellarium.
 

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