OPT's wide selection of refracting telescopes further plants our reputation as the telescope authority! The principal focusing element in a refracting telescope is a lens. Its curved primary (or largest) lens gathers light, bends it, and sends it back to a focal point where it is further modified by the use of another set of lenses called the eyepiece. The curvature and size of the primary lens dictate the amount of distance needed to achieve the focal point. There are a few different types of refractors in the world of astronomy. Apochromatic. Achromatic, Doublet, Triplet, and Petzval are all different types.