This was the world’s largest working telescope for over 30 years and was built entirely at the site with local labour and it expanded our universe.
Between 1845 and 1917, the large 72-inch telescope in what was then Parsonstown (now Birr) in the middle of Ireland was the world’s largest construction of a mirror telescope. It was used with the original mirror until 1878. It was built by the third Earl Rosse (1800–1867) and with it he was able to discern that the nebula M51 had a spiral structure and thus was not just a cloud of dust and gas in the then-known universe made up of the Milky Way. That the nebula had a structure pointed in the direction that it was a separate galaxy far beyond our own. The M51 is today called the Whilpool galaxy.
The huge telescope is beautifully situated in the park of Birr Castle, where the seventh Earl Rosse now cares about the historical heritage. The heritage also includes the extensive work that Lady Rosse devoted to improving the photographic technique, as well as the sons who were allowed to serve in the workshop and by the telescope. It is remarkable to note that the huge 6-foot mirror was constructed on site in the small rural town.
Today, the old telescope is supplemented by an ambitious science centre and since a few years it is also the location of the radio telescope I-LOFAR, which is part of a network of radio telescopes around Europe. On September 20, in the presence of Ireland’s Minister of Justice and Lord and Lady Rosse, the Center’s Director, Karl Grandin, being Chair of the European Physical Society Historic Site Committee was able to inaugurate the telescope as an such a site.