Terms: celestial pole, hour circles, diurnal circles
The SC002 star map is similar to a polar projection of the Earth's
north pole. The
celestial pole is at the center
of the map; around it is displayed the top cap of the celestial
Hour circles connect the poles
of the celestial sphere; here they are seen radiating out
from the north celestial pole (NCP). Diurnal circles,
are parallel to the celestial equator circle the pole.
The hour circles look like straight lines on the SC002,
but that's the sort of distortion projection can produce. Hour circles
really are great circles connecting the poles and diurnal circles
(except the celestial equator)
are small circles.