Coordinate systems. The following table lists the common coordinate systems in use by the astronomical community. The fundamental plane divides the celestial sphere into two equal hemispheres and defines the baseline for the latitudinal coordinates, similar to the equator in the geographic coordinate system.The poles are located at ±90° from the fundamental plane.

The history of astrometry is linked to the history of star catalogues, which gave astronomers reference points for objects in the sky so they could track their movements.This can be dated back to Hipparchus, who around 190 BC used the catalogue of his predecessors Timocharis and Aristillus to discover Earth's precession.In doing so, he also developed the brightness scale still …

Getting Started¶. The usual way to use astropy.time is to create a Time object by supplying one or more input time values as well as the time format and time scale of those values. The input time(s) can either be a single scalar like "2010-01-01 00:00:00" or a list or a numpy array of values as shown below. In general, any output values have the same shape (scalar or array) as the input.