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.
. Sobel, Dava . Dava Sobel . . Penguin . 1995 . 0-14-025879-5.