Firmamentum

The Firmamentum is a unique measurement and navigation instrument. Fully in the tradition of the historic watches used for observation, it not only measures the earth's rotation, thus giving the classic measurement of time, but with the aid of the hour angle it permits measuring the movement of the sun and planets in our solar system as well as that of the stars.

The hour angle based on the sun — the solar hour angle — can be simultaneously read off two displays. A unique mechanism with a variable-speed of gear train has permitted the second display to be designed such that it can immediately be changed over to display the hour angle based on the stars — the sidereal hour angle — by a pushbutton located at the 2 o'clock position.