n.1.(Astron.) An instrument, intended to represent the revolution of a comet round the sun.
References in periodicals archive ?
The Wayward Comet: A Descriptive History of Cometary Orbits, Kepler's Problem and the Cometarium
The cometarium turns the complex physics that underlies a comet's motion in space into the indomitable and certain roll of meshed gearing, he says, though in the end the tameness portrayed by the cometarium turns out to be a chimera; the comet is a beast that moves beyond the certainty encoded within finely interlocking gears.