ephem

ephem is a command-line utility that displays astronomical ephemerides, which are essentially tables of positions of celestial bodies. It allows users to calculate the positions of the Sun, Moon, planets, and other celestial objects for any given date and time. The software is often used by amateur astronomers, skywatchers, and educators to plan observations, understand celestial mechanics, and learn about the night sky.

The ephem program typically takes date and time input and outputs a set of coordinates for the requested celestial objects. These coordinates are usually expressed in various astronomical coordinate systems, such as the equatorial coordinate system (right ascension and declination) or the horizontal coordinate system (altitude and azimuth). The output can be customized to include specific objects, time intervals, and levels of detail.

While the core functionality of ephem is to provide positional data, some versions or related tools may offer additional features. These can include calculations for rise and set times, twilight times, phases of the Moon, and even basic predictions of occultations or conjunctions. The underlying astronomical calculations are based on established models and algorithms, ensuring a degree of accuracy for its intended purpose. Its simplicity and accessibility make it a valuable tool for anyone interested in the precise location of celestial bodies in the sky.