REFLECTING TELESCOPES

Reflecting telescopes, or reflectors, use only mirrors are are great for astronomy.  They consist of a primary mirror and a secondary mirror.  The light enters the optical tube and travels to the primary mirror of the reflecting telescope which is at the back of the tube.  The primary mirror is concave which forces the light to gather onto the smaller, and flat, secondary mirror at the front of the tube.  The secondary mirror does not magnify or focus the light at all, it merely redirects the light into the eyepiece. 

The biggest advantage to a reflector telescope lies in the fact that you can get a large primary mirror. They are supported from the back, so weight is not an issue like with a refracting telescope.  Remember, the larger the aperture, the more detail you can see and the brighter objects will appear. Also, the larger the aperture, the larger the potential magnification that can be achieved.

Of course, there are disadvantages to reflecting telescopes, as well.  The secondary mirror is right in the front middle of the optical tube. This causes it to block and somewhat distort the light that travels to the primary mirror.  Also, reflecting telescopes can be a bit more difficult to focus, but today's technology is making it a bit easier.  In terms of ease of use, reflecting telescopes require more preparation than a refracting telescope. They must be collimated, or aligned, or you will not achieve a crisp image.  There are however, collimating eyepieces that make this task much easier.  Collimating a catadioptric telescope is more difficult than a reflecting telescope.