The convex, or refractive lens at the and of a refracting telescope refracts, of bends, light as it enters the glass and focuses is on a single plane. This causes the image to appear upside down, but the concave lens on which the image is focused makes it appear upside right. By using a refracting telescope, the image can appear not only closer, but also brighter and clearer.

While Galileo refracting telescopes are still widely used today, they offer a limited field of view. For example, the Chabot Space and Science Center in Oakland, California houses an eight-inch and a 20-inch refracting telescope. Their simplicity may also shows signs of spherical aberrations. Achromatic lenses, developed in 1773, uses a convex lens and a flat lens placed together to help reduce spherical and chromatic problems.

Working To Keep Colors Together

The biggest problem with a refracting telescope is that during the refracting of the light, the color spectrum tends to separate during the light bending process. This is referred to as chromatic aberration and, although using concave and flat lenses together, creating an achromatic lens has reduced this problem, it is still a concern in larger lenses. A 26-inch telescope in Washington, D.C. is one of the largest in the country.

Although glass for lenses as large as 40-inches has been cast, they have not been used due to the imperfections in the glass distorting the color rays as it passes through. The importance of have the entire spectrum hit the focal place at the same time and in the same position is what has stopped refracting telescope construction for professional use.

Some observatories still use a refracting telescope and many private users find them useful for astrology observations as the lens’ position within the enclosed tube can provide a steadier image as opposed to a reflective telescope that counts on mirror reflecting the image from the objective lens to the eyepiece. As light from an image enters it will be reflected by the primary mirror to a secondary mirror and then to the eyepiece.

In addition, there are two types of telescopes. One type of telescope is called the refractor telescope and the other is known as the reflecting telescope. The difference between these two telescopes is how the light is captured.

Refracting and Reflecting Telescope

The refracting telescope obtains the light through its objective that is made out of glass. Basically, in this type of telescope, the glass lens is situated towards the front of the telescope. As the light is captured by the objective, it is then refracted or deflected through a lens which allows for the viewed image to be magnified. Examples of this type of telescopic equipment include scopes that are used on rifles, binoculars and spyglasses.

A reflecting telescope uses a mirror as its objective. This mirror is located towards the distal end of the telescope. In addition, the mirror has a concave shape. The curvature of the mirror allows for the midpoint of the mirror to be the focal point for all of the light that strikes each part of the surface of the bowl-like mirror. This reflection is then captured by the lens to view the item of interest.

Advantages Of The Reflecting Telescope

There are several advantages to the use of a reflecting telescope. The major advantage is that distortion of what is being viewed is minimal. This is because, through the use of the mirror, the wavelengths are all reflected consistently. This advantage also leads to the reflecting telescope being less expensive than the refracting telescope.

In addition, through the use of the mirror as the objective, the support for this mirror can be all along the posterior portion of the telescope. This allows for the housing to be very large which will accommodate a larger mirror. Larger mirrors mean more light which results in increased visibility.

Disadvantages

However, as with anything else, there are a few disadvantages in the use of a reflecting telescope. One of those disadvantages is size. This is due to the fact that these types of telescopes can accommodate larger mirrors. This results in the telescope itself being larger which may prove to be an issue when storing or relocating the reflecting telescope.

In addition, because of the use of mirrors, there may need to be occasional adjustments made so that optimum light alignment is maintained.

To see beyond what astronomers can see using traditional telescopes, which count on visible light for their viewing, a radio telescope is designed to hear the sounds from outer space as opposed to the sights. Most designed as a parabolic antenna, a radio telescope allows the user to listen to sounds emanating from sources in space.

Most people with an interest in space have probably heard of the Search for ExtraTerrestrial Activity (SETA), which is a group of people monitoring space for signals with a radio telescope that may indicate life from outer space. To date there has been no success in isolating sounds from space that can be blamed on extraterrestrial sources, except of course in movies.

Neutral hydrogen and carbon monoxide are examples of radio waves picked up with a radio telescope, along with other sources of electromagnetic signals picked up as sound. The first radio telescope in use was back in 1937, a dish about 30-feet in diameter, with interest growing ever since and the first arrays being put in use in the 1950’s. Today, the largest is the 1894-foot diameter RATAN600 in Russia.

Sound From Space Sparks Science Fiction Imagination

With the ability to receive sound signals from space picked up on a radio telescope, the imagination of writers and amateur star gazers have fueled by beliefs that some of the sounds are being created by other life in space. Continual argument persists on the existence of life in space and signals not readily identified is used as questionable indications of extraterrestrial life.

A very large array of radio telescope dishes in New Mexico boasts 27 dish antenna, each with a diameter of about 82 feet. They work in tandem searching the skies for sounds, acknowledging that considering the speed of sound is much slower than the speed of light, any sound picked up could be from yesterday or hundred of years ago.

Under construction in Western Europe is a low frequency array radio telescope, which will consist of 25,000 smaller antenna designed to develop radio pictures of the sky based on the origins and current location of the sources of sounds picked up by the array. Clusters of antenna will be spread out over an area approximately 220 miles square. With the added power to pull in radio signals from space it is hoped a better map of this galaxy and adjacent galaxies can provide a better understanding of the space being lived in.