Astronomer :: Astronomer (n.) One who is versed in astronomy; one who has a knowledge of the laws of the heavenly orbs, or the principles by which their motions are regulated, with their various phenomena..
Astronomy :: Astronomy (n.) The science which treats of the celestial bodies, of their magnitudes, motions, distances, periods of revolution, eclipses, constitution, physical condition, and of the causes of their various phenomena..
Astronomy :: Astronomy (n.) A treatise on, or text-book of, the science..