Optical astronomy is the branch of astronomy that studies celestial objects and phenomena visible to the naked eye or through telescopes that use visible light. There are several synonyms for optical astronomy, including visual astronomy, observational astronomy, and opto-astronomy. Visual astronomy refers to the observation of celestial objects using the naked eye or through telescopes that use visible light. Observational astronomy encompasses all methods of observing the universe, including those that use other forms of electromagnetic radiation such as radio waves and X-rays. Opto-astronomy, on the other hand, emphasizes the importance of optics and the use of telescopes in studying celestial objects. Regardless of the term used, all of these synonyms refer to the study of the cosmos through the observation of visible light.