what are the uses of a cassegrain and refractor telescope?

Answer 1

Refractors, telescopes that use only lenses, excel at terrestrial viewing, lunar viewing, planetary viewing, star cluster viewing, and astrophotograpy of stars, star clusters, planets, and the moon.

They are especially desirable for observing stars because they have no central obstruction held in place by support bars, so stars appear as perfect dots and not as "stars" with what are known as diffraction spikes. They are desirable for planetary and lunar viewing because they offer high contrast images. They are also more rugged than other types of telescopes.

The full benefits of a refractor can only be had if it's apochromatic though. Good refractors are very expensive.

There are many different types of cassegrains, however, they all share in common a folded design, and a central obstruction held in place by a glass plate at the front of the telescope. Different cassegrains are ideal for different things, but in general, they have long focal lengths so also do very well on planetary viewing, and again stars will have no diffraction spikes when viewed with them.

Cassegrains are an economical alternative to refractors, and like refractors, can easily be made large enough for deep space viewing. Their folded design also means they are more compact that other types of telescopes.

Answer 2

The Cassegrain telescope is a compound reflecting telescope with a concave primary and a convex secondary. Among the advantages of this design are a tube assembly that is shorter than the telescope's focal length, and the ability to correct for more aberrations than a Newtonian reflector (because it has two optical surfaces). Virtually all modern observatory telescopes are a variant of this design called a Ritchey-Chretien. Another variant, the Schmidt-Cassegrain telescope (SCT) is very popular with amateurs for their compactness and adaptability. The SCT , the Maksutov-Cassegrain, and the Meade RCX are called catadioptric designs, meaning a combination of lenses and mirrors, These all have some sort of corrector lens at the front of the telescope. Apertures from 90mm to 16 inches are readily available.

Refractor telescopes are popular with amateur astronomers for both visual observing and astrophotography. With modern glass types, the chromatic aberration (smeared colors) of traditional achromatic refractors can be completely eliminated. Telescopes with this type of correction are called apochromats and are much more expensive than achromats. Apochromatic refractors are best at wide-field astrophotography. Refractors are more expensive and more cumbersome than reflectors of the same size, and are seldom seen in apertures over six inches.

Answer 3

Binoculars are considered refractors.

So...looking at distant objects whether on Earth or sometimes in space if the object is large or close enough (moon, Jupiter, Saturn, Orion Nebula, etc)