Look at a light source through the space between your index finger and thumb. Have students sketch what they see. Astronomers study stars by looking through telescopes. Telescopes make stars and planets look bigger. Telescopes let us see two stars that are close together like Mizar A and Mizar B. Telescopes also let us see stars that are too faint to be seen with the eye.
Astronomers also study stars by passing their light through a glass prism or a diffraction grating.
Planets shine with reflected light. Planets move around stars. The time from one new Moon to the next is the Moon's synodic period . This is where our month comes from. As the Moon travels around the Earth it always keeps the same face toward the Earth.