Stars trails over Armazones

Multiple-exposure picture taken looking west from the top of the 3046-metre-high Cerro Armazones, the selected site for the European Extremely Large Telescope (ELT). Because of the rotation of the Earth, the night sky is seen as it rotates around the southern celestial pole. As a result of this movement, the stars describe dotted trails when a series of exposures is combined. The closer we look to the celestial equator — here seen near the left edge of the picture — the straighter the trails appear. On the right of the image is the Differential Image Motion Monitor (DIMM), used to measure the atmospheric seeing.