Noun
jovilabe (plural jovilabes)
(astronomy, historical) A scientific instrument used to determine the orbital periods of Jupiter's moons and to compute the times of their eclipses.
A 1984 Jovilabe showing Jupiter and the 14 then known moons required 14 turntables and 324 gears; it is accurate to within 0.01% *Fixed central rod, with top drive and sun and planet gearing. Source: Internet