coordinates, projected on the celestial sphere, are analogous to the geographiccoordinatesystem used on the surface of Earth. These differ in their choice of
position in the ecliptic coordinatesystem, convert to the equatorial coordinatesystem, and convert to the horizontal coordinatesystem, for the observer's
2307/2306514, JSTOR 2306514 Bell, Robert J. T. (1914), "49. The shortest distance between two lines", An Elementary Treatise on Coordinate Geometry of Three Dimensions