In the northern hemisphere, viewers will always be able to see certain stars and constellations in the northern circumpolar sky,[2] while same holds true for the southern hemisphere with respect to certain stars and constellations in the southern circumpolar sky. The celestial north pole, currently marked by Polaris, always has an azimuth equal to zero. Its altitude for a given latitude Ø is fixed and its value is given by the following formula: A = 90° - Ø.