Star clock
A star clock is a method of using the stars to determine the time. This is accomplished by measuring the Big Dipper's position in the sky based on a standard clock, and then employing simple addition and subtraction. This method requires no tools; others use an astrolabe and a planisphere.
A clock's regulator can be adjusted so that it keeps the Mean Sidereal Time rate. When it is then set to an observer's Local Mean Sidereal Time then a star will transit the meridian at the sidereal time of the star's Right Ascension.
