Khan Academy
Khan Academy: Angular Measure 2
Looking for an easier way to do angular measurements? This page introduces you to a trick by using skinny triangles with small angles. The skinny triangles lets the astronomer assume right triangles and then they can use trigonometry to...
NASA
Nasa Star Child: What Is a Light Year and How Is It Used?
This is a definition and example of how distance is measured in astronomy, such as the distance between our earth and the stars.