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Telescope Buyer’s Guide
There’s a lot of technical terms being thrown around in these reviews, so it may benefit you to brush up on some of the features to look for when purchasing the best telescope for your needs. Here’s a quick breakdown of some terms you’ll often see and how they’ll relate to your stargazing experience.
Aperture: The most important feature within a telescope is its aperture, the diameter of the main lens or mirror which light enters through. A model’s aperture determines how bright and sharp an image appears, so the bigger the better. Bigger apertures allow you to use more magnification.
Focal Length and Ratio: Focal length, which is expressed in millimeters or inches, determines its angular field of view. The focal ratio is found by dividing a telescope’s focal length by its aperture. Models with a higher focal ratio are generally better for high-magnification viewing.
Magnification: Magnification is one the most misunderstood specifications within a telescope. Experts say magnification range is nearly infinite, but it all depends on the type of eyepiece you use. A telescope normally lists a range of values for its useful magnification because too much power just makes images look fuzzy. If a specific model doesn’t list its useful magnification range, a good rule to find the max value is 50x your telescope’s aperture in inches and 2x its aperture in millimeters.
Type of Telescopes: Telescopes fall into three categories: refractors, reflectors and composites, also called catadioptric models. In refracting telescopes, the front, or objective, lens focuses light to form an image in the back eyepiece. Refractors typically produce clear, high-contrast images that are suitable for high magnification. A reflecting telescope uses a mirror to gather and focus the light. These models offer significant value in terms of more aperture for the money. Compound telescopes use both mirrors and lenses to gather an image, and are often compact and transportable. Catadioptric models are usually the most technologically advanced and versatile telescopes.
Keep these terms in mind when comparing prices and features to find the best home telescope for you.