40-foot telescope
English reflecting telescope, built 1785–1789
About
William Herschel's 40-foot telescope, also known as the Great Forty-Foot telescope, was a reflecting telescope constructed between 1785 and 1789 at Observatory House in Slough, England. It used a 48-inch (120 cm) diameter primary mirror with a 40-foot-long (12 m) focal length (hence its name "Forty-Foot"). It was the largest telescope in the world for 50 years. It may have been used to discover Enceladus and Mimas, the 6th and 7th moons of Saturn. It was dismantled in 1840 by Herschel's son John Herschel due to safety concerns; today the original mirror and a 10-foot (3.0 m) section of the tube remain.
Nearby
More to see within walking distance
Old Etonians F.C.
Association football club in England
0.9 mi away
Slough Town Hall
Municipal building in Slough, Berkshire, England
0.4 mi away
Herschel Park
Park in Slough, Berkshire, England
0.4 mi away
Slough Cricket Club
Cricket club based in Berkshire, England
1.2 mi away
Observatory House
Municipal building in Slough, Berkshire, England
Heart of Slough
Urban redevelopment scheme in Slough, England
0.2 mi awayPlaces to eat nearby
Finding places to eat…
Traveler reviews
Tickets & tours
Tickets and tours for 40-foot telescope
We may earn a commission from some of these links, at no extra cost to you. Learn more
Photos from Unsplash, Wikipedia and Wikimedia Commons (CC BY-SA); facts from Wikipedia; maps © OpenStreetMap contributors, weather from Open-Meteo. Huginn’s tips are AI-written — check prices, hours and entry rules before you go.