Types of astronomical telescopes (telescope types) vary by the optics used to magnify and direct the EMR, and by the portion of the EMR spectrum they observe. Telescopes also vary by the sensors and instruments they use to collect data, but often include a choice of sensors/instruments and common telescope classification terms are most often not based upon the sensors. Some classification terms refer to the telescope's purpose.
The EMR spectral band gives rise to terms such as radio telescope, X-ray telescope, etc. The optics is generally either refractive (using lenses or the equivalent) or reflective (using mirrors or equivalent reflectors, a reflector telescope). Many of the terms refer to the arrangements or shapes of mirrors or reflectors, some of which are applicable to and used for radio telescopes as well as UVOIR telescopes:
Off-axis telescope is a general class, presumed by some of these types and optionally incorporated in some others. The Wolter telescope design is specifically aimed at X-rays and gamma rays, using only incident optics, i.e., such that all its reflections modify the ray-direction over small angles. Some telescope classification terms based on various other characteristics, design elements and/or purposes: