There are two basic kinds of telescopes for the backyard observer, reflector and refractor, and they differ in the way they gather and focus light onto the eyepiece. The type discussed in this article will be the reflector telescopes. These telescopes use a series of large and small mirrors to bend and amplify the light from the stars and planets. It’s hard to imagine that by just using mirrors you will be able to see the rings of Saturn or the pinwheels of distant galaxies – but that is how it works.
There are two basic designs of reflector telescopes – the Newtonian and the Cassegrain. The Newtonian design was first created by Sir Issac Newton, the noted physicist of the 17th century. He concluded from his work in optics that the lenses of the period always suffered from the dispersion of light into colors (called chromatic aberration). In 1668 he built the first Newtonian Telescope using a mirror as the objective to bypass the problem of the chromatic aberration.
This design is quite simple and very popular with novice stargazers. There is usually one large mirror at the base of the telescope tube which focuses the image onto another flat mirror that then sends the image to the eyepiece where it can be magnified.
The second design is the Cassegrain type. This design uses a concave primary mirror at the base of the telescope with a convex secondary mirror facing it at the top of the tube. The light comes in through the top of the telescope and is reflected by the primary mirror onto the smaller mirror. This mirror in turn sends the light back through a hole in the primary mirror to the eyepiece. This design is slightly more complex and therefore more expensive, but both work very well.
Advantages Of Reflector Telescopes
The reflector telescope is a good all-around telescope and has several advantages over the refractor type telescopes. On the pro side, the design of reflector telescopes is somewhat less intricate than that of refractor telescopes. This usually makes these telescopes less expensive, at least on the lower end. It also allows more magnifying power in a more compact design. The larger models really give more value for the money compared to refractor telescopes. The fast focal ratio makes reflector telescopes very effective for viewing faint objects deep in space.
Disadvantages Of Reflector Telescopes
Although the reflector telescope is a good all-around telescope especially for the amateur astronomer, it is not without some drawbacks. The alignment of the mirrors is somewhat delicate and transportation can be a problem if not done very carefully. The mid-size to larger versions of these telescopes tend to be bulkier than the refractor models. The lower end models tend to produce a distorted image and there is a considerable amount of maintenance involved in cleaning and aligning the mirrors.
As with any telescope, there are always pros and cons to consider when looking to purchase. The reflector telescopes are effective and simple to use making them the best deal for amateur astronomers and star gazers. It is definitely worthwhile to consider a reflector telescope when you are researching which telescope will be right for you.