In the early 1840s, William Parsons, the Third Earl of Rosse, designed and built the largest telescope in the world. With this telescope, he discovered the spiral nature of some of the galaxies, and from 1845–1914, anyone wishing to witness this phenomenon had to come to Birr Castle.

This reflecting telescope remained the largest in the world for over 70 years and is arguably the largest historic scientific instrument still working today. The Leviathan of Parsonstown remains in the centre of the demesne as Ireland’s greatest scientific wonder and represents a masterpiece of human creative genius.

The Science Centre demonstrates how this extraordinary telescope was built in the castle workshops by the people of Birr. This touchscreen focuses on the casting of the three tonne mirror, by which peat-fired furnaces were used to heat three iron crucibles containing 1.5 tons of a tin and copper alloy, and the laborious and time-consuming process of grinding and polishing. The interactive offers the user three languages—English, French and German.
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