Name of projection to firmamentum (celestial sphere)

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Discussion Overview

The discussion revolves around the terminology associated with the projection of celestial objects onto the firmamentum, or celestial sphere. Participants explore whether this projection has a specific name and delve into related concepts such as celestial coordinates and historical perspectives on celestial mapping.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant inquires if there is a special name for the central projection of a star's position to the celestial sphere.
  • Another suggests terms like "Celestial Position" and "Celestial Coordinates," referencing right ascension and declination.
  • A participant mentions orthogonal projection and compares it to gnomonic projection, noting the lack of a specific name for the projection from space to a sphere.
  • It is proposed that the projection is simply referred to as a "projection," as it involves reducing dimensions by eliminating one coordinate.
  • Some participants reflect on the historical context, suggesting that medieval astronomers may have had various names for such projections.
  • A later reply references Hipparchus and his contributions to celestial mapping, indicating a historical depth to the discussion.

Areas of Agreement / Disagreement

Participants express differing views on whether the projection requires a specific name, with some arguing it is trivial and others suggesting historical significance. The discussion remains unresolved regarding the existence of a proper term.

Contextual Notes

The discussion highlights potential limitations in terminology and historical context, as well as the assumptions about the simplicity of the projection concept.

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TL;DR
Does the central projection of the position of a star to the firmamentum (celestial sphere) has a special name?
Does the central projection of the position of a star to the firmamentum (celestial sphere) has a special name?
 
Last edited:
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Celestial Position?
 
Celestial Coordinates? RA and Dec?
 
There is orthogonal projection from space to the plane.
I thought of something like gnomonic projection, but this is from the sphere to a plane. I find it strange that the more obvious projection from space to a sphere has no proper name.
 
Normally when you take coordinates and project them down to a space with smaller dimension by just eliminating one coordinate, you just call it a "projection". That's what's being done here. I don't know that it needs a special name, since it's such a simple concept.
 
Of course today we consider this trivial. But I thought that some medieval monks and arab sky mongers created thousand of strange names for it.
 
DrDu said:
Of course today we consider this trivial. But I thought that some medieval monks and arab sky mongers created thousand of strange names for it.
It was way before that. Hipparchus created the first map of the celestial sphere in the second century BC.
 

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