| The reflecting telescope built by William Parsons, the
Third Earl of Rosse, has a 72 inch diameter speculum metal mirror. The
telescope was put into use for the study of nebulae in 1845 and was the
largest telescope in the world until the time of the First World War.
The site of the telescope on the Earl's Demense in Birr,
County Offaly, Ireland ensured a steady supply of rain, and the sky was
clear enough for observations only one day in seven. Despite this, the
Earl's drawings of nebulae were excellent.
The telescope has recently been restored, with a new mirror,
a rebuilt tube and new ironwork. The new telescope is pointed with electric
motors, which replace the five men with hand-winches first used.