Hevelius' 150-foot telescope. This telescope was constructed by the German astronomer Johannes Hevelius (1611-1687). It was a tubeless telescope, with refracting lenses arranged along its length to achieve a focal length of 150 feet (45 metres). The design was a larger version of the type that Galileo had constructed. Hevelius built the telescope on the shores of the Baltic Sea, near his home town of Danzig. The lenses were suspended in a wooden trough supported by a vertical 90-foot (27 metres) pole, and operated by a team of workers and horses operating ropes and pulleys. The largest telescope at the time, it proved difficult to keep stable and was rarely used. Artwork published in Machina Coelestis (1673).