What is the angle measured in Celestial Navigation?

In celestial navigation, the angle measured is the angle between the visible horizon and celestial bodies. This measurement, known as the altitude, is crucial for determining a vessel's position on the Earth's surface. By measuring this angle using tools like a sextant, navigators can ascertain their latitude and, with additional calculations or observations, their longitude as well.

When observing celestial bodies such as stars, planets, or the sun, the navigator takes the angle from the horizon up to the celestial object. This elevation angle is fundamental in calculating one's geographic position, as it provides a reference point that can be used in conjunction with other navigational methods and tools. The accuracy of this angle affects the reliability of the navigation fixes derived from it, making it essential knowledge for anyone practicing celestial navigation.