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 sphere. Hour circles connect the poles of the celestial sphere; here they are seen radiating out from the north celestial pole (NCP). Diurnal circles, which 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.