The celatone was a device invented by Galileo Galilei to observe Jupiter's moons with the purpose of finding longitude on Earth. It took the form of a piece of headgear with a telescope taking the place of an eyehole.
Modern versions In 2013, Matthew Dockrey created a replica celatone, using notes from a version created by Samuel Parlour. From April 2014 to January 2015, Dockrey's celatone was on display in the Royal Observatory, Greenwich in east London.
See also Longitude prize Galilean moons
References
Sobel, Dava (1995). Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time. Penguin. ISBN 0-14-025879-5.
External links Video animation of a Celatone and its use in discovering the longitude for marine navigation Dockrey celatone "Apparatus to render a telescope manageable on shipboard"