REAs Essentials provide quick, easy access to essential information across a range of fields. These concise study guides summarize the essentials of the subject and are helpful for exam prep, homework, and as a lasting reference for students, teachers, and professionals. Astronomy Essentials covers the historical perspective of astronomy, sky basics and celestial coordinate systems, the origin and model of the solar system, the Sun and the planets, Keplers laws of planetary motion, planetary satellites, asteroids, eclipses, tides, stars, time, and binoculars and telescopes.