What is Epoch (astronomy)?
In [[astronomy]], an '''epoch''' (or sometimes '''epochal moment''') is a moment in [[time]] for which the position or the [[orbital element]]s of a celestial body are specified. The position at other times can be measured by taking into account [[proper motion]] or [[orbital motion]]. In the case of orbital elements for a [[solar system]] body, these change due to perturbation by other bodies in our solar system. {{Sci-stub}} [[Category:Celestial mechanics]]