[Solved] Currency-the amount of coins and bills in circulation-is the main liability of the Fed. Music Training: The education and practice of skills related to performing, understanding, and creating music. Amateur Stargazing: The hobby of observing celestial bodies, such as stars, planets, and moons, usually with the naked eye or with telescopes, without professional equipment or expertise. Astronomy: The scientific study of celestial objects, space, and the universe as a whole. Telescope: An optical instrument designed for the observation of remote objects by collecting electromagnetic radiation.