The equatorial sundial consists of a brass ring or hoop, which represents the celestial equator, and an adjustable armillary sphere that represents the celestial meridian. The sphere is oriented so that its axis aligns with the Earth's rotational axis, which is why it is called an "equatorial" sundial. The sphere has various rings and circles that are calibrated to celestial coordinates, allowing the sundial to be adjusted according to the observer's latitude and the date.
To use the equatorial sundial, it needs to be aligned with the North Star or the celestial pole for accurate timekeeping. As the Earth rotates, the sun casts a shadow on the brass ring, indicating the time of day. The position of the shadow corresponds to the position of the sun in the sky, and by reading the calibrated circles on the armillary sphere, one can determine the local solar time.
Chinese brass equatorial sundials were not only functional timekeeping devices but also works of art, showcasing intricate craftsmanship and often adorned with ornate engravings or inscriptions. They were utilized in important locations like palaces, temples, and observatories to mark the passage of time and coordinate various activities.