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 of 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. From April 2014 to January 2015, Dockrey's celatone was on display in the Greenwich Observatory in Greenwich, London.

gollark: Well, if I get a big enough pile, I can trade random copper-level stuff -> silvers -> golds.
gollark: Well, CB green coppers are more common than golds. If someone can't get a green copper for (roughly) the stuff I have, it'll be quite hard to add enough to get a gold.
gollark: That might be problematic, then.
gollark: Question: I've got a CB copper, cheese and paper; how many more similarly rare things do I need to get a CB gold?
gollark: I've taken it down now, because I'm too locked and kind of want to save up for a silver/gold, but it was brown.

See also

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.
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