Astronomy is a fascinating hobby. The heavens are so vast and beautiful that countless men have spent their entire lifetimes studying them. One of the first things that any astronomer needs is a good telescope, to allow them to see as much of the stars as possible.
How Does a Telescope Work?
It is a common misconception that the primary purpose of a telescope is to magnify the stars, making them larger and thus easier to see. While a telescope does magnify, the more important part of the telescope is that it brightens the image by bringing in more light, allowing you to better see what is being magnified.
There are many telescopes out there that advertise themselves as very powerful, offering as much as 500x magnification for little money. However, these telescopes are not very useful because they have small apertures that bring in little light. Images that you see in the telescope will always appear dark and indistinct.
There are two primary forms of telescopes, which brighten images in different ways.
Refracting Telescopes
A refracting telescope offers the sharpest images for the astronomer. It consists of a long tube with the aperture at one end and the eye piece at the opposite end. The tube narrows as it moves towards the eyepiece. This is the type of telescope that most people think of when they first think of a telescope.
The refractor works by gathering light through the aperture. (The higher the aperture, the more light can enter into the telescope). This light is sent through what is called the objective lens and focused as it travels through the tube. As the light is focused produces a sharp, clear image for the astronomer looking through the eyepiece. The image produced is upside down, however for the astronomer this is not an important matter.
Reflecting Telescopes
The reflecting telescope, like the refracting telescope, gathers light through the aperture. However, unlike the refractor it does not focus the light through a narrowing tube. The reflecting telescope is essentially straight, although there is some narrowing, and is thus larger and bulkier than the refracting telescope.
Unlike the refractor, a reflector does not have an objective lens. Light travels through the tube then is reflected off what is called the objective mirror at the end of the tube. This mirror is curved. The light then travels back up the tube, where it hits a second mirror. The second mirror reflects the light into the eyepiece, which sits near the top of the telescope.
The image produced in a reflecting telescope is not as great as that produced by a refracting telescope. However, for the same money a reflecting telescope can be purchased with greater aperture than one would get with a refracting telescope.
Reflecting telescopes are also called Newtonian telescopes, after Isaac Newton.