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.

Using a celatone.

Celatone by Matthew Dockrey. Museum at the Royal Observatory, Greenwich, UK.

Modern versions

In 2013, Matthew Dockrey created a replica celatone, using notes from a version created by Samuel Parlour.^[1] From April 2014 to January 2015, Dockrey's celatone was on display in the Royal Observatory, Greenwich in east London.^[1]

See also

• Longitude prize
• Galilean moons