Equinox (celestial coordinates): Difference between revisions

→‎Nutation: typo: oscilltaion -> oscillation
(contrast the other meanins of equinox in the lead paragraph even though there is a hatnote (since they are related, not just the same words), discuss the date of an equinox and epoch more clearly)
m (→‎Nutation: typo: oscilltaion -> oscillation)
=== Nutation ===
Nutation is the oscillation of the ecliptic plane. It was first observed by [[James Bradley]] as a variation in the declination of stars. Because he did not have an accurate enough clock, Bradley was unaware of the effect of nutation on the motion of the equinox along the celestial equator, although that is in the present day the more significant aspect of nutation.<ref>{{cite book |last=Barbieri |first=Cesare |authorlink= |title=Fundamentals of Astronomy |url= |accessdate= |year=2007 |publisher=Taylor and Francis Group |location=New York |isbn=978-0-7503-0886-1 |page=72 }}</ref> The period of oscialltaionoscillation of the nutation is 18.6 years.
==Equinoxes and epochs==