What contribution did Foucault make to astronomical observation?

Foucault was a famous French experimental physicist. He studied medicine and worked as a doctor for several years, and later turned to experimental research in physics. In 1845, he served as a science reporter for the "Debate" newspaper. He often wrote science columns and introduced new developments in contemporary science. At the same time, he also conducted physics experiments at his home. He studied photography and used it in astrophotography. His interest in the problem of pendulums and the rotation of the Earth originated from astronomical observations. In 1845, he collaborated with A.H.L. Fizeau and took photos of the sun. Later, he wanted to take photos of stars, which required long exposures. The telescope system should be able to continuously keep pointing at the target in the sky during the shooting process. . In order to control the movement of the telescope system so that it can track the target, Foucault made a special clock based on the design of a conical pendulum clock that Huygens had not realized in the 17th century. He supported the pendulum on a steel rod. During the experiment, he noticed that when the steel rod was clamped on the clamp of the lathe and the lathe was turned by hand, the vibration of the steel rod always maintained its original vibration plane and did not rotate with the lathe.