Star trails around the south celestial pole
auteur: Anglo-Australian Observatory/David Malin Images/Novapix
référence: a-pas01-10001
Image Size 300 DPI: 40 * 51 cm
By pointing a camera towards the south (or to the north in the northern hemisphere) at night, we can record the paths of stars which never set. They appear to circle the apparent position of the Earth's axis of rotation projected on the sky. The elevation of this position above the local horizon indicates our local geographical latitude, about 30 degrees south at Siding Spring. The angle swept out by the arcs is an indication of the exposure time, which was about 10.5 hours on 400 ISO colour film. This kind of exposure is only possible from an extremely dark site.