A Newtonian telescope is a type of reflecting telescope designed by Sir Isaac Newton in the 17th century. It uses a curved primary mirror to gather light and reflect it to a focus point, where an eyepiece lens magnifies the image. This design allows for a compact and efficient telescope, minimizing chromatic aberration, which is common in refracting telescopes. The Newtonian telescope typically features a simple structure, making it popular among amateur astronomers. Its open tube design allows for easy cooling of the mirrors, improving image quality. This telescope is versatile and can be used for both planetary and deep-sky observations.