Campanola CAN18 Instruction Manual page 42

Celestial north
pole
Meridian
Celestial equator
When an imaginary line through the earth's axis is extended, it
intersects the celestial sphere at two points. Celestial north pole is one
of the points that can be observed from the northern hemisphere. The
other point that can be observed from the southern hemisphere is
called the celestial south pole.
On the line where the celestial sphere meets the plane that includes
the celestial north pole, the zenith and the celestial south pole, this
is the area that is higher than the horizon. Within this, the area that
can be used to read the hour angle starting point or local sidereal
time is the range from the celestial pole that is visible (celestial north
pole in the case of the northern hemisphere), through the zenith and
toward the opposite celestial pole (celestial south pole in the case of the
northern hemisphere) until it reaches the horizon. When it needs to be
specifically distinguished from the north-south azimuth line on the
earth's surface it is called the "celestial meridian", but "meridian" alone
when used in astronomical observation is usually understood to mean
the meridian on the celestial sphere.
This is the intersecting line between the celestial sphere and the plane
that includes the point of observation, perpendicular to the earth's axis.
Brief explanation of astronomical terms
41