Sunset over La Palma observatory. Person watching the sun setting over the telescope array of the Roque de los Muchachos Observatory, La Palma, Canary Islands, with crepuscular rays appearing above the horizon. This observatory is situated 2,600 metres above sea level and is home to some of the world's leading research telescopes. Crepuscular ray are rays of sunlight that appear to radiate, through gaps in clouds, from the point in the sky where the sun is located.