Een zeesfeer van Michiel Coignet?

Abstract

A Nautical Sphere by Coignet Michiel?In 1580 the Antwerp mathematician Michiel Coignetdescribed the nautical hemisphere, an instrument with which the longitude problem could, in theory, be solved. In 2008 an example of this instrument, albeitincomplete, surfaced during an exhibition on the history of the Jesuit Seminaire de Tournai. This hemisphere is the only horizontal hemisphere known (two vertical hemispheres are kept in Firenze and in St-Andrews). All indications are that the Tournai instrument was made in Coignet's workshop.