Audio Guide：

The earliest telescope was a refracting telescope and appeared in the Netherlands in 1608. A convex lens is used to converge light waves to a focus, and another lens is used to magnify the image. In 1668, Issac Newton invented the reflecting telescope by using a concave lens to converge light rays. While the refracting telescope has clearer images, it suffers from chromatic aberration. Comparatively, it is easier to make reflecting telescopes. Larger reflecting telescopes can be made at lower costs to observe darker astronomical objects. That’s why modern large-scale telescopes are mostly reflecting telescopes.