Assertion: proper motion | /r/DefinedAs | angular changes per year
Facets:
value: alternatively
type: MANNER
value: in declination
type: LOCATION
value: in the star's right ascension
type: TEMPORAL
Source sentences:
text: Proper motion may alternatively be defined by the angular changes per year in the star's right ascension (μ α ) and declination (μ δ ), using a constant epoch in defining these.