A telescope magnifies distant objects. The types of telescopes are refractor, reflector or both. Light is made up of electromagnetic waves over a spectrum. Light interacts with objects by being reflected off them, passing through them and being refracted, and absorbed. Different frequencies of light interact with objects differently in a periodic manner. The incident ray is the incoming ray; the reflected ray is reflected light reflected by the object it is reflected from. Refractor telescopes are the simplest types of telescopes; they use lenses. They refract light to produce a magnified (virtual) image. It is not easily misaligned and its important components are not in contact with the atmosphere. However, it is impractical for larger apertures and they are normally expensive. It has 2 lenses: the objective and secondary (eyepiece) lenses.
Reflector telescopes, however, have a primary and secondary mirror to reflect the light. The light would enter the telescope, get reflected from the primary mirror into the secondary mirror, which reflects light into the eyepiece. Unfortunately, it is easy to misalign and is susceptible to "coma"s. It requires frequent cleaning and the secondary mirror blocks incoming light in the centre of the telescope. It is cheaper than a refractor telescope and allows for larger aperture areas.
The Alt-Azimuth mount has 2 planes of motion and is suited for scanning. It is the simplest mount too and can move diagonally. The equatorial mount can move along planes of ascension and declination. It can track stars in the night sky. It is used for long periods of observation and deep-sky photography.
You can screw on filters onto the eyepiece. They block out certain wavelengths of light. Examples of telescope filters include the solar filter, chromatic aberration, light pollution reduction, deep sky and planetary set filters. They can increase contrast in objects you are viewing with your telescope, or protect your eyes from the sun. The planetary set filters are useful for viewing the planets of the solar system.
Eyepieces contain a lens element inside a housing, with a "barrel" at one end. The shorter the eyepiece, the higher its magnification. It is focused by turning a knob mechanism, and its length is measured in millimetres.
Extra accessories for a telescope include the barrow lens, focal reducer and the finder scope. The barrow lens increases its magnification more, while the focal reducer reduces the magnification but allows for a larger field of view. The finder scope has a lower magnification to allow you to scan the sky for the object you are looking for, and is useful for reflector telescopes.
I feel happy after this lesson, as it had given me a more in-depth knowledge of telescopes and I had learnt about how the length of eyepieces affect the magnification of the telescope. The shorter the eyepiece, the greater the magnification. A telescope's normal maximum magnification is 180x. Moreover, I learnt about the barrow lens, and how it can increase the telescope's magnification even further.
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| A refractor telescope in Allegheny Observatory in the University of Pittsburgh, Pennsylvania. Credits to Niagara on Wikimedia Commons. Image was licensed under CC BY-SA 3.0. |
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| An old reflector telescope. The image was released into the Public Domain. The picture was originally made on 1 January 1912. It was originally published by the Popular Science Pub. Co. in New York. |
You can screw on filters onto the eyepiece. They block out certain wavelengths of light. Examples of telescope filters include the solar filter, chromatic aberration, light pollution reduction, deep sky and planetary set filters. They can increase contrast in objects you are viewing with your telescope, or protect your eyes from the sun. The planetary set filters are useful for viewing the planets of the solar system.
Eyepieces contain a lens element inside a housing, with a "barrel" at one end. The shorter the eyepiece, the higher its magnification. It is focused by turning a knob mechanism, and its length is measured in millimetres.
Extra accessories for a telescope include the barrow lens, focal reducer and the finder scope. The barrow lens increases its magnification more, while the focal reducer reduces the magnification but allows for a larger field of view. The finder scope has a lower magnification to allow you to scan the sky for the object you are looking for, and is useful for reflector telescopes.
I feel happy after this lesson, as it had given me a more in-depth knowledge of telescopes and I had learnt about how the length of eyepieces affect the magnification of the telescope. The shorter the eyepiece, the greater the magnification. A telescope's normal maximum magnification is 180x. Moreover, I learnt about the barrow lens, and how it can increase the telescope's magnification even further.
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