Mount Wilson solar tower observation room. This observation room is at the base of the 46-metre (150-foot) solar tower at the Mount Wilson Observatory. The tower was built in 1912 but is still used today to observe the Sun. Mirrors in the tower reflect and magnify the sun, producing a 42 centimetre diameter projection in the observatory room. The reflected light is analysed using a spectrograph, which measures the different wavelengths of radiation emitted by the Sun. The Mount Wilson Observatory sits at an elevation of 1742 metres within the San Gabriel mountain range in California, USA.