Definition of prime vertical in English:

prime vertical


  • A great circle in the celestial sphere passing through the zenith and the east and west points of the horizon.

    • ‘Regiomontanus, however, is based upon an equal division of the equator rather than the prime vertical - it is the same method as that suggested by Morinus, but bows to convention by commencing from the ascendant.’
    • ‘For star observations a star should be selected which will be about three hours from the meridian and near the prime vertical at the times of observation.’
    • ‘For the observations closer to the meridian than the prime vertical, make the calculation of latitude with the estimated longitude.’