Determining the Absolute Parameters of the Meridian Circle by Observing the Prime Vertical——I. The Absolute Determination of Azimuths

The circumpole star一azimuth mark method to be used to determine azimuths on the meridian circle is not suitable for the areas at lower latitudes.In this paper a method of determining azimuths by observing the prime vertical is proposed.If three times when a star passes across the directions of the prime vertical and the meridian of an instrument, which may be used to observe the star not only in the prime vertical direction but in the meridian direction, are recorded, the azimuth of the instrument in the meridian direction may be determined.This method by which short observing time is needed makes the observations very convenient, and the azimuths determined are absolute.