Uploaded July 2010 | Updated September 2026, 3 weeks ago
The Horizon System is used to locate things on the great sphere around us that includes the sky as well as the unseen stars below the horizon. Zenith (the point straight overhead) and the ideal horizon provide one zero point for these coordinates. The other zero point is the meridian, which is the great circle that runs through both the Zenith and the celestial poles (which are determined by the apparent rotation of the celestial sphere about the earth).
The Horizon System is used to locate things on the great sphere around us that includes the sky as well as the unseen stars below the horizon. Zenith (the point straight overhead) and the ideal horizon provide one zero point for these coordinates. The other zero point is the meridian, which is the great circle that runs through both the Zenith and the celestial poles (which are determined by the apparent rotation of the celestial sphere about the earth).
