Reflector telescopes

Mirror (reflectors)

— a key design element of any reflector is a concave mirror that plays the role of a lens. Such telescopes are simpler and cheaper than refractors (see the relevant paragraph), they have a shorter length, while the lens size can be much larger, and the image is more reliable, with virtually no colour distortion. The last two features make it possible to comfortably use reflectors for observing deep space objects. On the other hand, such models require rather delicate handling and are sensitive to thermal stabilization: before the observation begins, the telescope must cool (or warm up) to the ambient temperature, otherwise noise may occur due to the difference in air temperatures. In addition, concave mirrors distort the shape of objects at the edges of the field of view, which can cause inconvenience in astrophotography; however, this shortcoming is not critical and can be easily compensated.