welcome to Marine Courses Center today we will talk about celestial navigation concept of celestial sphere for astro navigation

Celestial equator ( Equinoctial )

Is the great circle on the celestial sphere, perpendicular to the axis of rotation and divides the celestial sphere into Northern and Southern hemispheres.

Celestial meridians

 Parallels of declination (Diurnal circle )

  Small circles on the celestial sphere, and parallel to the equinoctial.

 Concept of celestial sphere

Vertical circles 

 Observer’s meridian

Is the great circle on the celestial sphere passes through celestial poles, Zenith and Nadir points, it divides the celestial sphere into eastern and western hemispheres.

 it is divided into :-       PZP’    the upper observer‘s meridian

                                         PZ’P’   the lower observer’s meridian  

Principal Vertical circle

Is the great circle on the celestial sphere passes through Zenith and Nadir points and  celestial poles.

Prime Vertical circle

Is the great circle on the celestial sphere passes through Zenith, Nadir, East and West points.
         (it is perpendicular to Principal Vertical circle at zenith point)

The elevated pole represents the latitude
 of the observer

try to answer this question