Mirror telescopes (reflectors) consist of two mirrors: the primary mirror collects the light, while the secondary mirror – also called the secondary – deflects light from the primary mirror to a focal point position accessible by the observer.

Depending on the design, different mirror shapes are used. The most important forms are spherical, parabolic, and hyperbolic.

Depending on the mirror shape, the following optical systems are the result:

• Newtonian telescope: parabolic primary mirror, flat secondary mirror
• Schmidt-Cassegrain telescope: spherical primary mirror, spherical secondary mirror, Schmidt plate
• Maksutov telescope: spherical primary mirror, spherical secondary mirror, meniscus lens
• Ritchey-Chrétien telescope: hyperbolic primary mirror, hyperbolic secondary mirror
• Cassegrain telescope: parabolic primary mirror, hyperbolic secondary mirror