There's no historical record of a device called a "star clock" being invented. It's possible this is a misunderstanding, or a term used for a specific type of astronomical tool that doesn't have a commonly accepted name.

Here's why:

* Clocks are time-keeping devices. They measure the passage of time using a regular, repeating motion.

* Stars are used for navigation and astronomical observations. Ancient cultures used them to track seasons, predict celestial events, and find their way around.

However, star charts and astronomical tools can help determine time by observing the position of stars in the sky.

Here are some potential scenarios:

* You may be thinking of an astrolabe: A medieval instrument used for navigation and measuring celestial angles. Astrolabes can be used to determine the time of day based on the position of the Sun and stars.

* A celestial globe: A model of the celestial sphere that shows the position of stars and constellations. These can be used to track the movement of stars and constellations over time.

* A star clock might be a fictional device from a book or game.

If you can provide more context about where you encountered the term "star clock," it might be possible to clarify its meaning.