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

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SUMMARY

The discussion centers on the mapping of celestial coordinates to geographic coordinates, specifically questioning whether a standard correspondence exists. It is established that Right Ascension (RA) corresponds to longitude and declination corresponds to latitude, with the vernal equinox serving as the zero-point at 0° N, 0° W. The celestial coordinate system was created by projecting Earth's longitude and latitude onto the celestial sphere. Tools like Stellarium can visualize this mapping, allowing users to see constellations based on their geographic location.

PREREQUISITES
  • Understanding of celestial coordinates, specifically Right Ascension and declination.
  • Familiarity with geographic coordinates, including latitude and longitude.
  • Knowledge of the Earth's rotation and its impact on celestial observations.
  • Basic skills in using planetarium software like Stellarium.
NEXT STEPS
  • Research the celestial coordinate system and its historical development.
  • Explore the functionality of Stellarium for visualizing celestial objects from different geographic locations.
  • Investigate different map projections, such as the Mollweide projection, and their applications in astronomy.
  • Learn about other planetarium software options for celestial mapping and visualization.
USEFUL FOR

Astronomy enthusiasts, educators, and anyone interested in the relationship between celestial and geographic coordinates will benefit from this discussion.

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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