Telescope Information

Reflector telescopes are the short and fat ones. They use a concave mirror to reflect and focus light back from the “back” of the telescope onto a secondary flat mirror which then reflects the light to the side and into the eyepiece. The eyepiece then focuses and magnifies the image.

Reflector telescopes have much larger telescope tube diameters, this allows a lot more light to enter the telescope. Because of this they are best suited for astronomical use and are not great for terrestrial observation.

Catadioptric Telescopes

Compound or catadioptric telescopes are hybrid telescopes that have a mix of refractor and reflector elements in their design. The first compound telescope was made by German astronomer Bernhard Schmidt in 1930. The Schmidt telescope had a primary mirror at the back of the telescope, and a glass corrector plate in the front of the telescope to remove spherical aberration. The telescope was used primarily for photography, because it had no secondary mirror or eyepieces -- instead, photographic film was placed at the prime focus of the primary mirror. Today, the Schmidt-Cassegrain design, which was invented in the 1960s, is the most popular type of telescope; it uses a secondary mirror that bounces light through a hole in the primary mirror to an eyepiece.

Refractor Telescopes

Refractor telescopes are "telescope shaped" in that they are long and thin. They have an objective lens at the front of the telescope and the eyepiece at the back. As the light passes through the telescope it is bent or refracted, into a focal point. The eyepiece then magnifies the image for the eye to see.

The power or magnification is changed by inserting different eyepieces. As well they can be adapted so that an SLR camera can be attached to the telescope by using a ‘photo adapter tube’ (available separately). Although the image is shown upside down and back to front, if you add an ‘erecting eyepiece’ (supplied with the telescope) the image is “flipped” the right way round. You would use this if you wanted to look at a terrestrial object such as a distant building.

There are two different common types of telescope mounts. The Alt-Azimuth mount and the Equatorial mount.

Alt-Azimuth mounts are simpler and cheaper. They are made around a“U” shaped yolk which allows the telescope to move in two directions - Altitude (or up and down) and Azimuth (or side to side). Some Alt-Azimuth mounts have “slow motion” controls which allow the user to follow an object by rotating them. Alt-Azimuth mounts are very simple to set up and operate, even for beginners. The Tasco Galaxsee 525 uses an Alt-Azimuth mount.

Equatorial mounts are more complex and more expensive. They can be set in precise polar alignment and can be set to allow for the Earth's tilt. This means that you are able to track stars and planets as the Earth turns.

They have "setting circles” which let you locate stellar objects that are too dim to be seen with the naked eye. Most equatorial mounts can even be fitted with electric motors, called clock drives, which will automatically rotate the telescope to compensate for the motion of the Earth. The Tasco Galaxsee 375 uses an Equatorial mount.