Optical astronomy is a branch of astronomy that deals with the observation of celestial objects using visible light. It is the oldest form of astronomy, and has been practiced for thousands of years. Optical astronomers use telescopes to collect and focus light from celestial objects, and then analyze this light to learn about the objects' properties.

Optical telescopes can be divided into two main types: refracting telescopes and reflecting telescopes. Refracting telescopes use lenses to focus light, while reflecting telescopes use mirrors. Reflecting telescopes are generally more powerful than refracting telescopes, and are therefore used for most professional astronomical observations.

Optical astronomers study a wide variety of celestial objects, including stars, planets, galaxies, and nebulae. They use optical telescopes to measure the brightness, color, and spectra of these objects, and to determine their distances, sizes, and masses. Optical astronomers also use telescopes to search for new planets and moons, and to study the atmospheres of planets.

Optical astronomy has played a major role in the development of our understanding of the universe. It has allowed us to learn about the properties of stars, planets, and galaxies, and to understand the evolution of the universe. Optical astronomy is still a vital field of research, and continues to make important contributions to our knowledge of the universe.