Physics - The Telescope and What It's Good For

Telescopes or binoculars enable us to observe objects located at a very far distance. From the point of view of optics, microscopes also belong to the family of telescopes. With microscopes, we are able to view very small objects, often not visible to the human eye.

There are many types of telescopes. The Dutch or Galileo's telescope uses a converging lens with a large focal point distance for the objective (the lens closest to the observed object) and a diverging lens for the ocular lens (the lens located closest to our eye) which, together, offer the observer a direct (unreversed) image of the object. Telescopes of this type are often constructed in duplicate and in which the flow of light rays are divided prior to their entry into the ocular but diverted to two separate oculars, a design used for opera viewers or binoculars (lesser magnification).

With Kepler or star gazing telescopes, used above all in astronomy, the ocular and the lens are made up of one or more converging lenses. Such devices magnify the object being viewed but reverse it by 180°, which can then be corrected back to normal using another set of lenses. However, this complex system of lenses results in a major loss of light, which is why star gazing telescopes no longer use this technology.

Terrain or ground telescopes, which serve to observe objects located on the ground, have a third converging lens located between the objective and the ocular lenses. This third lens reverses the image so that the final image visible to the human eye is right side up.

Prismatic telescopes are those which use two prisms, located between the objective and ocular lenses, instead of a converging lens to reverse the image back to normal. Here, one prism reverses the upper and lower ends of a flow of light beams, where the other prism reverses the left and right ends, to generate a final image which appears right side up when viewed through the ocular.

Distance is measured using infrared rays. This type of measuring is accomplished by using an emitter of infrared rays and a receiver located at a certain point. The measured distance is then calculated by comparing the phases of the reflected and directly received (reference) rays.

The principle of the telescope is a fine example of the many uses one can find for optical lenses and shows us that, with the help of various types of lenses and their organisation, we can view objects and phenomena not visible to the human eye.

Types of Telescopes: Modern Versions

Telescopes have been around for hundreds of years and their birth is commonly associated with Galileo although in reality Hans Lippershey, Zacharias Janssen and Jacob Metius all laid claim to inventing earlier models. These "original" telescopes that were created are still mostly what people associate with when they think of telescopes but it is a universe away from what modern telescopes have evolved into.

This original telescope design is known as Refracting or Refractor telescopes and consist of a singular tube that light passes down in a straight line to the eyepiece. These types of telescopes are still around today but they have some limits in modern astronomy. They are rugged, great for lunar or planetary viewing and good in light polluted urban areas, but are limited when used for deep space viewing. Because the lenses are expensive to produce the modern consumer is a world away from buying a powerful, high quality refracting telescope. They also have other negative aspects associated with them in that they are often bulky and space consuming. The images viewed through refracting telescopes are also subject to color aberrations around the edges of the viewed object.

These problems were solved in 1733 by Isaac Newton who built the first reflector or reflecting telescope. Today these are also known as Dobsonian or Newtonian telescopes. These telescopes utilize mirrors to reflect light out a side opening to the eyepiece. Modern reflectors provide bigger bang for your buck because mirrors are cheaper to produce meaning they come with wider apertures. They are superior for viewing deep space images. They do come with drawbacks however. They are not as durable as their refractor counterparts and they require more maintenance. In addition to this the mirrors may need recoating after a number of years.

The new kid on the block these days is a hybrid design utilizing lenses and mirrors. These modern telescopes are based on a design, which was developed by Bernhard Schmidt and they have all the positive attributes of both refractor and reflector telescopes. This design is used in a range of scopes from small amateur backyard versions to professional observatory models. The one and only drawback is that they tend to be more expensive than the other two types of telescope.

Telescopes have come an incredibly long way in both design and technology since their formative years. Today a lot of modern telescopes are computerized and you view the image on your screen. The control interface allows the user to move and save co-ordinates in their computer so they can easily view the same point repeatedly. Computer controlled versions also allow photographic and video recording of the night sky.

Today it is easier than ever to get into astronomy and is an especially positive experience to share with the family. Decent introductory telescopes can be purchased online or at good department and specialty stores for under $300. These will let you introduce your kids to the night sky and give them a good appreciation of the cosmos. If you want to educate your kids more there are several Internet sites that are hooked up to more powerful telescopes in observatories around the globe. You can logon and in some cases control these telescopes from their website and get the feel of having your own observatory with having to leave your home or spend any money.