Editing Orbital node (section)

==Planes of reference==
Common [[plane of reference|planes of reference]] include the following:
* For a [[geocentric orbit]], [[Earth]]'s [[equatorial plane]]. In this case, non-inclined orbits are called ''equatorial''.<ref name="darlinglon">{{cite encyclopedia |url=http://www.daviddarling.info/encyclopedia/L/line_of_nodes.html |title=line of nodes |encyclopedia=The Encyclopedia of Astrobiology, Astronomy, and Spaceflight |first=David |last=Darling |access-date=May 17, 2007}}</ref>
* For a [[heliocentric orbit]], the [[ecliptic]] or [[invariable plane]]. In this case, non-inclined orbits are called ''ecliptic''.<ref name="darlinglon" />
* For an orbit outside the [[Solar System]], the plane through the [[primary (astronomy)|primary]] perpendicular to a line through the observer and the primary (called the ''[[plane of the sky]]'').<ref>{{cite web |url=http://astrowww.phys.uvic.ca/~tatum/celmechs.html |title=Chapter 17 |work=Celestial Mechanics |first=Jeremy B. |last=Tatum |author-link=Jeremy B. Tatum |access-date=May 17, 2007}}</ref>