What are the kinds of telescope?

Answer 1

Optical TelescopesReflecting (mirrors)

Refracting (lenses)

Catadioptric (combination of lenses and mirrors)

Radio TelescopesFixed antennae

Phased array

Movable dish

X-ray TelescopesGamma ray Telescopes

Answer 2

• Refractors - Refractors have a long, thin tube, and use a glass lens to gather and focus light. Refractors are sturdy, require little maintenance, and have sealed tubes to prevent dust or air from interfering with viewing. Larger refractors produce clear, high-contrast images, and smaller models are popular as starter telescopes because they're also inexpensive. Refractors can reveal details of the planets and the moon, even when viewing them under city lights. However, because refractors generally have small apertures, they may not work well for viewing faint, distant objects like galaxies and nebulae. Refractors can also be used for daytime land viewing, particularly if used with a "correct image" diagonal, instead of the "star diagonal" (or right angle mirror) usually used.

• Reflectors - Reflectors were designed specifically for astronomy, and use a concave mirror located at the back end of the telescope's tub to gathers and focus incoming light. Reflectors are large and have a fat tube; they are also heavier and bulkier than many other kinds of telescope, and the mirror alignment must occasionally be adjusted. However, they are popular with amateur astronomers, because it is less expensive to make a big mirror than to make a big lens, which is what refractors use, and so it is relatively simple to make a reflector. Reflectors are ideal for viewing everything from nebulae to galaxies, but are not recommended for land viewing because they create upside-down or rotated images. This isn't as much of a concern for astronomy.

• A catadioptric optical system - one where refraction and reflection are combined in an optical system, usually via lenses (dioptrics) and curved mirrors (catoptrics). Catadioptric combinations are used in focusing systems such as search lights, headlamps, early lighthouse focusing systems, optical telescopes, microscopes, and telephoto lenses. Other optical systems that use lenses and mirrors are also referred to as "catadioptric" such as surveillance catadioptric sensors.