... ESO, the European Southern Observatory . ... Survey Telescopes . ... ESO 50 Years . ... A celebration was held at the APEX [1] base station in Sequitor, San Pedro de Atacama, to mark ten years of astronomical research with the APEX telescope , which resides on ChileтАЩs Chajnantor Plateau , 5100 metres above sea level. From there, the telescope observes the sky in submillimetre wavelengths , giving astronomers access to the coldest regions of the Universe, which cannot be seen in visible light. ...