Celatone

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.

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.

• Longitude prize
• Galilean moons

• 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.

• 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"