This group gathers mechanical engineering inventions built to measure or display the passage of time or the positions of celestial bodies, including mechanical clocks and watches, chronometers, sundials, the telescope, the orrery that models the solar system, the astrolabe and nocturnal used for celestial navigation and night timekeeping, the hourglass and water clock, and the pendulum mechanisms that regulate them. Their shared work is tracking time or the sky through mechanism rather than electronics, as distinct from the tools and measuring instruments gathered separately for physical quantities such as weight, temperature or wind.