In its simplest terms, an optical telescope is one that is designed to collect light in the visible spectrum of electromagnetic radiations. In other words, light that can be seen with the eyes rather than through using specialized equipment. This is done through the use of lenses and mirrors which collect the light and create an enhanced image for the viewer.
Mainly there are three types of optical telescopes:
1. Refracting telescopes, also called dioptric, which uses lens to gather light.
2. Reflecting telescopes which use mirrors to form the image, also known as catoptrics which is another term for using mirrors and reflections.
3. And finally there are catadioptric telescopes which use both lenses and mirrors together.
A telescope’s ability to gather light and resolve small detail is directly related to the primary lens or mirror that collects and focuses the light. The larger the primary lens is, which is also called the objective, the more light the telescope can collect and the clearer the image will be.