This lesson provides a basic introduction to celestial navigation for navigators, sailors, and others interested in the topic. It begins with the relationship between celestial coordinates and Earth coordinates and examines key celestial navigation parameters—geographic position, sextant altitude, observed altitude, azimuth, and computed altitude—that can be used to identify to a ship's position. A U.S. Navy navigator demonstrates the main celestial sights performed over the course of a day, including the morning three-star fix, morning Sun line, Local Apparent Noon Sun line, afternoon Sun line, and evening three-star fix, and demonstrates how the sight reduction culminates in a marked intercept and line of position on a navigation plot. The concepts of fix, running fix, estimated position, dead reckoning, and assumed position are also discussed. Although no formal background is needed for this lesson, some familiarity with the basics of navigation and the Universal Plotting Sheet will be useful to the learner.