Telescopes

Telescopes come in three varieties: Refractors, Newtonian Reflectors, and Catadioptrics. Each kind of telescope collects and focuses light so that it can be magnified or recorded, but each does so differently. All perform well when properly designed and manufactured, but each has its own special advantage.

Catadiaoptric telescopes utilize a combination of lenses and mirrors. Refractors incorporate lenses, and Newtonian reflectors use mirrors.

Choosing a particular telescope depends on your requirements. Before buying, you should consider what you plan to use the telescope for now and in the future. Many amateurs own two or more telescopes to satisfy their varied interests.

Click here for commonly used terms and characteristics of telescope and click here for descriptions of common optical aberrations.

Telescope Performance

At Scope City we are often asked "What is the most powerful telescope I can buy?" - That depends on what you want to view and how you measure power.

"Power" generally refers to magnification. When viewing the countryside, the Moon or the planets, magnification is great. Magnification is a function of a telescope's focal length and the focal length of the eyepiece in use (normally measured in millimeters "mm"). But magnification is not always beneficial in astronomy. For example, when viewing nebulae and galaxies, a lower-power, wider-field scope, that can reveal dim objects, is more important.

"Light Grasp" is a measurement of how much light a scope can gather at any given instant. Light grasp is a function of the aperture of the telescope's main lens. A large aperture telescope can reveal dimmer astronomical objects better than a high magnification telescope can.

Click here for a table that compares scope apertures, listed both in inches and millimeters, with the associated Light Grasp, Magnification limits and Limiting Visual Star Magnitudes.

Another way to measure the performance of a telescope is to measure how often it is used. Ask yourself which is more valuable, a small portable scope that is enjoyed weekly or a giant telescope that sits in the closet and is used maybe once a year? The right telescope for you is a balance between magnification and the light gathering power of the optical system. It depends on you; and how you plan to use your telescope.

At Scope City we want to help you purchase the right telescope.