Cassegrain Reflector

Introduction to Cassegrain Reflector

Generally, a telescope is a device used to observe space, Stars, etc. It is manufactured in different mirrors like convex, concave, and their combination, etc. Earlier, we refracted telescopes. But these were replaced entirely by the Cassegrain reflector telescope by providing sharp and high contrast images. Let us understand the working principle of a Cassegrain reflector telescope.

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Working Principle of Cassegrain Reflector

The Cassegrain reflector works on a unique principle to give images effectively. Generally, the Cassegrain reflector is designed to combine one primary concave lens and one secondary convex lens. Also, a mirror is replaced in the place of the lens in its design. With the presence of a mirror, which is lightweight, the Cassegrain reflecting telescope produces parabolic aberrations instead of spherical aberrations. The parabolic Miller has a hole in its Center, and from there, the electromagnetic waves were captured and sent to secondary convex lens edges in hyperbolic form. 

As the name of our telescope itself tells that it has a reflection, the received electromagnetic waves were sent back to the hole, which is termed as an eyepiece and reaches the focal point. The two-way direction of electromagnetic waveforms a fold at the focal point. This force gives the highest focal length and bright, sharp magnetic image than any other telescope.

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Classification of Cassegrain Reflecting Telescopes

There are two types of casa grande reflecting telescopes. Both of these telescopes have very slight differences. They are - 

1. Maksutov-Cassegrain Telescopes: these are also known as Mak telescopes. In these telescopes, a simple spherical curve will be there for the primary lens, and the secondary lens has a thin layer of aluminium. This type of telescope was easy to design and manufacture. It doesn't require any alignment and is also compact and versatile with very few chromatic aberrations.

2. Schmidt - Cassegrain Telescopes: these are known as SCTs. It is an ideal method used by many people to explore the sky and planetary systems, which is specially designed and placed a figure lens at the starting part of the tube. Also, placing a piece of fulfilment at the plane gives a large aperture.

Advantages of Cassegrain Reflecting Telescope

The Cassegrain reflecting telescope has several benefits because of its nature. Some of those benefits are - 

  • In this telescope, the mirror is replaced by an objective lens. So there is no chance for chromatic and spherical aberrations.

  • The spherical aberration will be converted into parabolic aberration.

  • The appearance of the image in a reflecting telescope is brighter than that of the refracting telescope.

  • Another advantage of a Cassegrain reflecting telescope is, it requires only one side of polishing the image.

  • The lens is heavier than the mirror. So because of using lightweight mirrors, the apparatus requires less support.

These are some of the advantages possessed by a Cassegrain reflector.

Newtonian Cassegrain Telescope

Whenever we hear the name of Isaac Newton, we always remember gravitational force. He also worked on the light and its waves. In this process, he got mixed up with using a refracting lens. He wants to avoid chromatic aberrations and wants to try something different than the refracting lenses. 

He tried to use a copper and tin mirror instead of placing a lens as it is very cheap and produces tons of light with more sharpness and brightness. In the Newtonian Cassegrain telescope, the light is collected at the top of the tube and the other endpoints towards the sky. The lower part of the telescope will be in a spherical or parabolic shape. The celestial bodies emit the waves.

The image captured by the primary lens can be reflected in the secondary lens and vice versa. This can be done with a 90° angle. The whole experiment was done in the 16th century. How wonderful it is! Still, everyone is eager to use the principle as well as the telescope.


Hence the Cassegrain reflector is an ancient model used to detect the images from sky, Stars, planets, etc., at an affordable price. Several scientists did experiments and found new things which are beneficial to future generations. So everyone should understand the value of these studies and make worth of these experiments.

FAQs (Frequently Asked Questions)

1. What are the Limitations of Reflecting Telescopes?

Ans: The reflected telescopes are far better and beneficial than those refractive telescopes. Even though they have several benefits, few limitations were all so accompanied by the reflecting telescope. Let's see those few limitations.

  • The reflecting telescope may not produce all the rainbows and moonbeams when compared to the refracted telescope.

  • Due to the shadows produced by secondary mirrors during reflection, there are many chances for the obstruction of light and waves. 

  • The alignment of mirrors will become an abstraction for the new bees. Even though it is negligible for experienced people, it should be considered as a drawback.

These are the few limitations faced by people while using the reflector telescope. Also, these limitations cannot be faced while using the refracting telescopes.

2. What are the Three Basic Types of Telescopes?

Ans: The telescope is an instrument used to observe and detect the images of space which include stars, planets, celestial bodies, etc. Even though the function of the telescope is the same, the working principles and design of manufacturing May differ from one type to another. We have three different types of telescopes. They are as follows- 

  • The optical telescope is a basic telescope that is used to observe the planets and the Galaxy with a breasted eye from an eyepiece.

  • Refracting telescope is also known as a dioptric telescope. In this telescope, the light enters from one end of the telescope and reaches the other end through refraction. During the process of refraction, light bends and gives a heavy and bright image. That's the reason the refracting telescope has a large aperture.

  • Reflecting telescope is the ideal one that is used widely. It is also known as a catoptric telescope. In this, the same working principle is followed like a refracting telescope. But the reflection process takes place, and a mirror replaces the lens. Due to the reflection, the electromagnetic waves reflect the other end of the lens and produce thin, sharp, and bright images with a 90o angle.