Birr Castle telescope

Two tower walls were build so the 3 ton mirror and its tube could be moved to view different parts of the sky. Due to the positioning of the towers, and the earths rotation, viewing of stellar objects were limited to a short time frame of 50 minutes to 2 hours.

For much of its existence, the 72 inch telescope was focused on nebula and star clusters. Sometimes, it was able to see spiral arms on what was previously viewed as gas clouds. These spiral nebulas would eventually be called spiral galaxies. The Earl’s research help to establish that these spiral nebulas were not made of gas but individual stars, residing out side our own milky way galaxy.

Given the Irish weather and its limited tracking capacity the ordinal telescope had an amazing list of achievements. The mirror, being made from metal, tarnished quickly from Irelands humid climate. Never the less, with regular maintenance the telescope was keep in use through generations. It was only after the death of the fourth Earl of Rosse that the telescope was dismantled its usefulness having been replaced by larger telescopes else where.