Galileo's sketches showing the movement of Jupiter's moons.
Note the numbering.
Another drawing of Jupiter and moons
Galileo's sketches of the moon.
Compared to modern photos:
A simple drawing of the Pleiades - an easy-to-find constellation. Note how Galileo indicates the major stars by drawing them larger. Also, this shows how we began to understand how many more stars were visible through a telescope than with the unaided eye because of the light-gathering capabilities of the "objective lens."
For comparison, here are modern photos of the same stars.
Same constellation with individual stars named:
Just for fun:
Astronomer/artist Chesley Bonestell's famous painting of Pleione, flattened because of extreme rotation speed.