Editing Proper motion (section)

== History ==

Proper motion was suspected by early astronomers (according to [[Macrobius]], ''c.'' AD 400) but a proof was not provided until 1718 by [[Edmund Halley]], who noticed that [[Sirius]], [[Arcturus]] and [[Aldebaran]] were over half a degree away from the positions charted by the ancient Greek astronomer [[Hipparchus]] roughly 1850 years earlier.<ref name=Neugebauer>{{cite book |title=A History of Ancient Mathematical Astronomy |author=Otto Neugebauer |url=https://books.google.com/books?id=vO5FCVIxz2YC&q=proper+motion+angle&pg=PA1085 |page= 1084 |isbn=978-3-540-06995-9 |publisher=Birkhäuser |date=1975}}</ref><ref>{{Cite journal |date=1719-12-31 |title=I. Considerations on the change of the latitudes of some of the principal fixt stars |url=https://royalsocietypublishing.org/doi/10.1098/rstl.1717.0025 |journal=Philosophical Transactions of the Royal Society of London |language=la |volume=30 |issue=355 |pages=736–738 |doi=10.1098/rstl.1717.0025 |issn=0261-0523}}</ref>

The lesser meaning of "proper" used is arguably dated English (but neither historic, nor obsolete when used as a [[postpositive adjective|postpositive]], as in "the city proper") meaning "belonging to" or "own". "Improper motion" would refer to perceived motion that is nothing to do with an object's inherent course, such as due to Earth's [[axial precession]], and minor deviations, nutations well within the 26,000-year cycle.