Ptolemy quotes (in Almagest III.1 (H195)) a description by Hipparchus of an equatorial ring in Alexandria; a little further he describes two such instruments present in Alexandria in his own time.
Ptolomej navodi (u Almagestu III.1 (H195)) Hiparhov opis ekvatorijalna prstena iz Aleksandrije, a malo dalje i opisuje dva takva instrumenta prisutna u Aleksandriji u njegovo vrijeme.