Birr Castle, the Earls of Rosse and the Giant Telescope

The question at the time was whether the faint smudges of light in the sky were gaseous in nature or large numbers of stars that were beyond the resolution of the best telescopes of the day. This was the problem that the third Earl of Rosse set out to answer when he built the largest telescope in the world at his family's country seat in the middle of Ireland. Before the "Leviathan of Parsonstown" was built the cudos of owning the largest instrument rested with William Herschel but the title remained in Ireland until the 100 inch Hooker telescope saw first light in 1917.