Keplerian refracting telescope

A Keplerian refracting telescope is a type of optical telescope that utilizes a lens as its objective to form an image. Refracting telescopes typically have a lens at the front, then a long tube, then an eyepiece or instrumentation at the rear, where the telescope view comes to focus. Originally, telescopes had an objective of one element, but a century later, two and even three element lenses were made.