A periodical publication of astronomical data useful to a navigator is called:

• A. Almanac
• B. Ephemeris
• C. Nautical Almanac
• D. Astronomical Almanac

Answer: (A)

A periodical collection of astronomical data used for navigation is called an almanac. The general term fits because an almanac compiles data such as celestial positions, rising and setting times, and other events that help someone determine their position at sea or on land. While navigators often rely on a Nautical Almanac for specific maritime use, the broad category you’re identifying is the almanac. An ephemeris is a set of positions for celestial bodies, typically a component within such publications, and Astronomical Almanac is a particular annual title within the same family of data, with Nautical Almanac being the navigationally oriented edition.