A refracting telescope consists of

A refracting telescope is an optical instrument that uses lenses to gather and focus light [1]. It typically consists of two convex lenses: a large objective lens with a long focal length to collect light from distant objects, and a smaller eyepiece lens with a shorter focal length to magnify the image. These lenses must have unequal focal lengths to achieve magnification, which is calculated as the ratio of the focal length of the objective to that of the eyepiece. While some early designs like the Galilean telescope used a combination of a convex objective and a concave eyepiece, the standard astronomical refractor (Keplerian) utilizes two convex lenses of different focal lengths to produce a magnified image. Reflecting telescopes, by contrast, primarily use mirrors.

Sources

1. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 10: Light: Mirrors and Lenses > A step further > p. 156