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Ephemeris: 03/17/2025 – When the largest telescope in the world was in Ireland
This is Ephemeris for St. Patrick’s Day, Monday, March 17th. Today the Sun will be up for 12 hours and 1 minute, setting at 7:51, and it will rise tomorrow at 7:49. The Moon, 3 days past full, will rise at 11:40 this evening.
In the 19th century Ireland laid claim to having the largest telescope in the world. It was a reflecting telescope with a mirror diameter of 72 inches. It was built by William Parsons the Third Earl of Rosse. The base of the telescope tube rested in a pit between two massive walls and could only look to either side of a north-south direction. It saw first usage in 1847. The telescope was called the Leviathan of Parsonstown, and was in use until 1890. Mirrors in those days were made of a silvery alloy called speculum. Two mirrors were used alternately because speculum tarnished. The mirror not in use would have to be re-polished and swapped in from time to time. It was the largest telescope until the 100 inch at Mt. Wilson was put in service in 1917.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
03/17/2014 – Ephemeris – When Ireland had the world’s largest telescope
Ephemeris for St. Patrick’s Day, Monday, March 17th. The sun will rise at 7:51. It’ll be up for 11 hours and 59 minutes, setting at 7:51. The moon, 1 day past full, will rise at 9:11 this evening.
In the 19th century Ireland laid claim to having the largest telescope. It was a reflecting telescope with a mirror diameter of 72 inches. It was built by William Parsons the Third Earl of Rosse. The base of the telescope tube rested in a pit between two massive walls and could only look in a north-south direction. It saw first usage in 1847. The telescope was called the Leviathan of Parsonstown, and was in use until 1890. Mirrors in those days was made of a silvery alloy called speculum. Two mirrors were used alternately because speculum tarnished. The mirror not in use would have to be re-polished and swapped in from time to time. It was the largest telescope until the 100 inch at Mt. Wilson was put in service in 1917.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The 72 inch Leviathan of Parsonstown. source: http://www.klima-luft.de/steinicke/ngcic/persons/rosse3.htm
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