Lick Observatory. Time exposure image showing star trails over a telescope dome at the Lick Observa- tory on Mount Hamilton in California, USA. In the foreground are trails from red torches carried by astronomers so that their night vision is not affected. Completed in 1888 at an altitude of 1280 metres, Lick was the world's first permanent mountaintop observatory. Its location provided excellent viewing conditions for years until light pollution from the nearby city of San Jose began to interfere with results. In 1997 the observatory is operated by California University. Star trails are caused by the apparent motion of the stars due to the rotation of the Earth about its axis.