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.
A treatise on, or text-book of, the science.
From the GNU version of the Collaborative International Dictionary of English.
astronomy
/ə-strŏn′ə-mē/
noun
From the GNU version of the Collaborative International Dictionary of English.
Are you saying that observing the Earth should count as astronomy?
Technically correct. The best kind of correct.