This volume serves as a comprehensive reference tool for calculating the precise positions of celestial bodies and predicting astronomical phenomena for the year 1991. The publication is compiled by astronomical observatories to provide standardized data for navigation, surveying, and scientific research. It utilizes rigorous mathematical models to track the movements of the Sun, Moon, planets, and stars throughout the calendar year.

This publication is recognized as a foundational technical resource for professional astronomers and navigators requiring high-precision data. Readers frequently note the extreme density of the numerical tables and the specialized knowledge required to interpret the provided ephemerides.