What is device used to determine the altitude of the North star?

The device used to determine the altitude of the North Star (Polaris) is called an astrolabe. An astrolabe is an ancient astronomical instrument that allows users to measure the angle of celestial objects above the horizon. By aligning the astrolabe with Polaris, one can determine their latitude based on the altitude of the star. This technique has been used for navigation and understanding one's position on Earth.