SAO star catalog
Whirlpool Galaxy M51
Ancient armillary sphere
Astrometry and celestial mechanics
Astronomy is separated into 3 traditional fields: astrometry and celestial mechanics are considered classical astronomical branches; astrophysics is the modern branch.
Astrometry was born to accurately mapping the positions of the "fixed" stars and recording the motions of the planets. It was most of what early astronomers did, including the ancient Greeks, long before Galileo, Kepler and Newton. Astrometry can be considered the oldest sub-field of science.
Celestial mechanics is about calculating orbital elements for planets and such and predicting their future positions. The "golden age" of celestial mechanics began in the 17th century with Galileo, Kepler and Newton.
Astrometry and celestial mechanics are so related that they may be considered a single branch: for this reason, the Scientia websites are only two, astrometry.org and astrophysical.org.
Astrometry and celestial mechanics have been important in history for sailing (maritime navigation), since navigators used to calculate their position on Earth upon the observation of stars.
Today, they are still important for keeping time.
Read more about Astrometry.
Read more about Celestial mechanics.
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