subject: Basic differences between reflecting and refracting telescopes [print this page] When looking at telescopes, and in particular astronomical telescopes one of the most important thing a beginner will want to know is whether they should buy a reflecting telescope or a refracting telescope.
Often this is personal choice but it helps at least to know the difference so in this article we will look at the very basic differences between the two types. At the least, you will know what a dealer or a web site is talking about when they mention the two types.
A reflecting telescope uses a system of internal mirrors to reflect and angle the image coming into the scope thereby effectively increasing the telescope's length. You view the image from the side of the scope which seems rather odd to some people but this is an easy way to spot a reflecting telescope. The aperture (in this case, the width) of the scope is the basic measure of how much light will get into it and how large the main (or objective) mirror is and the simple rule of thumb here is, the bigger the better! The actual magnification of these scopes is adjusted by the eyepiece you use when viewing the final image.
Refracting telescopes are based on the traditional eye glass design, at the simplistic level there is nothing majorly complicated happening here; the light comes in one end and is magnified by the lenses and you view it through the viewfinder end. Often there will be a 90 degree mirror at the end to make viewing easier and many people prefer this to the viewing position of the reflecting telescope. Other than that there is no real change from the original design that Galileo created. Because of the lack of any obstruction in the mirror path the image from a cheaper refracting scope will usually have a higher contrast than an equivalent reflector.
Reflecting telescopes do need their mirrors aligned on a regular basis whereas refractors are permanently aligned which means they are pretty much "ready to go" whenever you need one.
Basic differences between reflecting and refracting telescopes
