observātor — Lewis & Short
observātor, ōris, m.id.,
I a watcher, observer (perh. not ante-Aug.):
nemo observator, nemo castigator assistet,Plin. Pan. 40:
observator et custos bonorum,Sen. Ep. 41, 2: Catholicae legis, i. e. one who obeys it, Cod. Th. 16, 5, 1.