The Celatone was created for the Longitude Punk'd competition held by Greenwich Observatory. They asked for steampunk-themed artifacts inspired by the hunt for the longitude, as documented by the original letters of the inventors.
I chose to work from Samuel Parlour’s “apparatus to render a telescope manageable on shipboard”, which was itself a reinvention of a device described by Galileo, the celatone. The idea is that if you can see eclipses of the moons of Jupiter, that's like seeing a giant clock in the sky. And if you know what time it is, you can find the Longitude! Hooray! The rocking deck of a ship is no place for a telescope on a tripod, but what if you mount the telescope to a helmet of some kind? Note that there is no evidence that Galileo ever made one. It wouldn't have done him any good, as the astronomical charts of his era were nowhere near good enough. Also, well, it doesn't really work anyway.
As a result of the contest, the Celatone was on display at Greenwich Observatory (part of the National Maritime Museum in London) for most of 2014. More pictures can be found in this set.