[Physics Class Notes] on Optical Telescope Pdf for Exam

A telescope that is optical is a telescope that gathers and focuses light very keenly. It is mainly from the parts that are visible of the electromagnetic spectrum. That is to create a magnified image for the direct view or to make a photograph or we can say to collect data through electronic sensor image.

There are said to be three primary types of optical telescope that are:

• The refractors which use lenses are dioptrics.

• The reflectors that use mirrors are catoptrics.

• The catadioptric telescopes combine lenses and mirrors.

Reflecting Telescope

Telescope is a device that is used to form magnified images of objects that are distant. The telescope is said to be undoubtedly the most important investigative tool in astronomy. It provides a means of collecting as well as analyzing radiation which comes from celestial objects, even those which are in the far reaches of the universe.

The term is Galileo astronomy that was revolutionized when he applied the telescope to the study of extraterrestrial bodies in the early 17th century. 

Until then instruments magnification had never been used for this purpose. Since the work of Galileo’s pioneering that is increasingly more powerful optical telescopes which have been developed till date. We can say that as it has a wide array of instruments that is capable of detecting and measuring radiation in every region of the electromagnetic spectrum. The capabilities which are observational have been further enhanced by the invention of various kinds of instruments that are auxiliary that is the camera, spectrograph, and charge-coupled device and by the use of the electronic computers, the rockets, and spacecraft in conjunction with the system that is the telescope. 

Astronomical Telescope

The telescope astronomer makes use of two lenses that are positive lenses: the objective, which usually forms the image of the object which is distant at its focal length. And the eyepiece that generally acts as a simple magnifier with which to view the image that is formed by the objective. 

Its length is said to be equal to the sum of the focal lengths of the objective and eyepiece as well. And its angular magnification which is written as -fo /fe , giving an inverted image.

The telescope that is astronomical which can be used for terrestrial viewing but seeing the image that is in the position of upside down is a definite inconvenience. By viewing stars upside down direction there is no problem. A shorter telescope that is with upright viewing is said to be the Galilean telescope. 

[]

Types of Reflecting Telescopes

A telescope that is the reflecting one also known as a reflector is a telescope that uses a single or is a combination which is of curved mirrors that reflect light and form an image. The telescope which is reflecting was invented in the 17th century by sir Isaac Newton as an alternative to the refracting telescope. Which at that time was a design which suffered from severe aberration chromaticity. Although the telescope that is reflecting one produces other types of optical aberrations.

It is a design that usually allows for very large objective diameter. Almost all of the major telescopes which are used in astronomy research are said to be reflectors. 

The telescope which is reflecting comes in many designs and variations and may employ some extra elements that are optical to improve the image quality or we can say the place in the image in a mechanically position that is advantageous. Since the telescope that is reflecting use mirrors the design is sometimes referred to as the term “catoptric” telescope.

A primarily curved mirror is the telescope which is a reflector basic optical element that creates an image at the focal plane. The distance that is from the mirror to the focal plane is known as the focal length. The film or we say that a digital sensor may be located here to record the image easily or a secondary mirror which may be added to modify the optical characteristics or redirect the light to film. The digital sensors, or any other eyepiece for visual observation.

The telescope that is the reflecting is just like any other optical system that generally does not produce “perfect” images. The need to image objects which are at distances up to infinity is to view them at different wavelengths of light. Which is along with the requirement to have some way to view the image the mirror produces. This means that there is always some compromise in a reflecting telescope’s optical design.

Non Optical Telescopes

We notice that until the 1930’s all the observations astronomical had been made in the visible region of the spectrum that is the electromagnetic one. Although there are some of the scientists who had predicted that some objects in space should produce a spectrum that is continuous beyond the visible and yet no one had observed them. The discovery of the radio which was extraterrestrial sources was made by accident by Karl Jansky who was working for the famous Bell Laboratories in 1933. 

It was said that he was investigating a source of radio interference in short-wave radio transmissions that took across the Atlantic ocean. This was happening when he discovered that the noise was coming from the direction of the centre of the Milky way in the constellation Sagittarius. The first purpose that was for building a radio-telescope for observing radio sources emanating from space was in 1937. And since that time the field of astronomy which is of radio has become a fundamental area of research.