How Do Telescopes Work?

Wigberto L Maldonado Rodriguez

It is more often thought that telescopes are meant for the purpose of magnification in the night sky. While this is not always true, the important fact remains that telescopes are used for the purpose of accumulating light to enable scientists and astronomers to view faint objects with ease.

The main idea behind the telescope is that, it works by focusing the incoming light to the development of an image. This image is best viewed by means of an eye piece, which in turn acts as the magnifying glass. The opening through which light enters is referred to as the aperture and the presence of a larger aperture implies that light is gathered more. The light that enters is collected and is passed through a lens that is at the opening of the tube. This tends to bend the light together as a whole. From there, it is brought to a single point, termed as the focus that is exclusively designed to occur at the end of the wide tube, referred to the body. The eye piece actually remains slotted at the end of the telescope and features a slide in mechanism that helps to adjust the focus depending on the needs of the user. There are many other varieties of telescopes however the refractor design is the simplest and the one most commonly in use.

Reflectors were initially developed in the year 1680, the Reflectors are devices that are the result in correcting the chromatic aberrations that were developed. It employed the usage of a little curved mirror instead of a lens to gather the light and point it out to a focus. A modified version of the Reflector was developed in the year 1722 that featured parabolic mirrors and there were changes to the mirrors that were used. The Newtonian model is one of the most successful models of the telescope. Dobsonian reflector telescope is a type of the Newtonian model and is featured with a simple tube and have apertures ranging from six to 17 inches. They are more economical; however, the one disadvantage with a reflector telescope is to align the mirrors often.

Refractors were invented by Hans Lippershey and used by Galileo, the Refractors are a combination of concave and convex lenses. They essentially comprise three distinct parts and thus, employ the usage of lenses that do not correct achromatic aberrations to the max. To overcome this issue, these telescopes are features with lenses or that are “coated” or lenses that are made of fluorite glass to overcome the problem. Refractor telescopes feature good resolution that is ideal to see distant sky objects such as the planets and stars with ease. Their objective lenses are more than 4 inches in diameter and they are the costlier than the Reflector type on account of the lenses used. The basic principle behind these Refractors is the refraction of light, where light travels from a rarer medium towards a much denser medium and is represented by Snell’s Law; μ=Sini /Sinr Snell’s Law, the most common law that is used to describe the angles of refraction and incidence is also applied in a Refractor to explain the concept of chromatic aberrations caused due to dispersion. However, with the development of achromatic lenses, this phenomenon has reduced to a greater extent. There are many factors that are associated with the working of telescope such as the Aperture, the magnification, focal length and more.

Aperture refers to the most important section when buying a telescope. A telescope with a larger aperture implies that it can view objects that are faint with ease, unlike a telescope with a smaller aperture. It is measured in terms of mm in diameter and thus a telescope with a minimum of 120 mm aperture tends to gather as much as four times the quantity of light that enters through it. It is also referred to as the primary mirror aperture or that of the objective lens. The highest magnification that is used in the aperture is the theoretical limit and should not exceed more than that is required. When magnified too much, objects tend to move out of detail and thus clarity is lost. It is known that for every 1 mm of aperture opening, there is a magnification of two times. This is also referred to as the highest Practical power of the telescope. Focal length is the distance at which the telescope focuses on an image. There are eyepieces that tend to have varying focal lengths and thus it is a combination of the telescope focal length and the eye piece focal length that tends to deliver the possible magnification. There are eye pieces that come in varied focal lengths varying from 50 mm to 2mm and usage of multiple eye pieces will help to deliver magnifications at different lengths.