Proper motion may alternatively be defined by the angular changes per year in the star's right ascension (μα) and declination (μδ) with respect to a constant epoch.
pRoper motion MaY aLterNatiVely bE defineD BY THe anGuLaR chANges pEr yEar In th:e star's riGht AScension (Μα) and decliNAtiOn (μδ) with RespECt tO a Constant EpocH.