Telescope Buying Guide

Buying a telescope is tricky because there are so many things to consider. To get you started, here are a few of the most important:

Optical Design
A telescope's optical design refers to the way in which light is gathered and passed through the lens of the scope. There are two types of light gathering elements, called objectives: lenses and mirrors. We offer telescopes with both types of objectives in three different optical designs:

Refractor - Want to observe wildlife or look at geographic features? A refractor telescope, which uses a lens as its objective, is a good option. This type of scope is easy to use and not mechanically complex. Since there are not many parts, they hold up well under rugged use. Refractor scopes become increasingly bulky and expensive the better their light-gathering capabilities, but their simplicity and reliable design make them an excellent choice for beginners.

Reflector - Also referred to as Newtonian reflectors, this type of design uses a concave mirror as its objective. Unlike refractors, reflector-type telescopes are generally not suited for viewing land-based objects. They do, however, offer much more light-gathering power for the money and show celestial objects very well. Because of the way light moves through a reflector telescope, they are put to best use when right-side-up viewing is not important.

Catadioptric - Catadioptric telescopes use both mirrors and lenses. Combining the desired features of both objectives, these scopes are the most modern, popular and versatile option. There are two types of catadioptric designs:

Schmidt-Cassegrain telescopes can be slightly more expensive than Newtonian reflectors with the same light-gathering power. But, their overall superior design, durability and ease of use make them an excellent option when budgets aren't an issue.

Maksutov-Cassegrain telescopes have similar advantages and disadvantages to the Schmidt-Cassegrain design. In general, they are a bit heavier and have a smaller field of view, which makes them slightly less expensive.

A telescope's aperture may be the most important factor to consider when choosing a telescope. It controls how much light the scope can let in, which determines what objects you are able to see. Our Celestron telescopes have apertures (which are circular openings) ranging from 50 to 150 millimeters in diameter. The larger the aperture, the more light it lets in and the more types of objects you will be able to see.

Focal Length
The focal length of a telescope is the distance from the lens or primary mirror to the focal point. The longer it is, the more power and magnification it has. Concurrently, the longer the focal length, the smaller the field of view or amount of sky you will be able to see at once. The focal lengths of our telescopes run from 360 to 1500 millimeters.

Eyepieces magnify the image inside the telescope so that we can see it with our eyes. They come in different lengths, which determine their power. A low power eyepiece provides a greater field of view, while high power offers more magnification. The power scale is typically regarded as:

Up to 12mm: High power
12 – 25mm: Medium power
25mm and above: Low power

Some telescopes have more than one eyepiece, so you can use the power that's appropriate for what you're looking at. Many eyepieces are interchangeable, so you can buy additional ones to switch out when you need to. The eyepieces on our Celestron telescopes range from nine to 40 millimeters.

Magnification is often touted as one of the most important factors in choosing a telescope; but, since it is a result of the relationship between the focal length of the scope and the eyepiece, it's best to focus on those two features. Doing so will give you more control of the field of view as well as the telescope's magnification.

A telescope's mount supports the tube and allows it to move up and down and from side to side. There are two types of mount: altitude/azimuth (or Altizimuth) and Equatorial.

Altizimuth - This is the simplest type of mount. It's perfect for looking at land-based objects and celestial bodies at low powers. Look for one with slow-motion controls to help you point your scope smoothly at a precise location.

Equatorial - Equatorial mounts are ideal for long-exposure photography because their horizontal axis is tilted so that it's parallel to the earth's axis of rotation. Since one axis is fixed, it's easy to track a moving object through the sky. This kind of mount is also often equipped with setting circles to help locate celestial bodies using coordinates. Some are motorized so that the scope can automatically follow an object in motion.

Peripherals & Accessories
Aside from telescope mechanics, there are a few other things you'll want to consider when making your purchase.

Finderscopes - Finderscopes are small, low power telescopes attached to a main telescope for the purpose of locating a specific object. It usually has a wide field of view and crosshairs (or a red light) so that once the finderscope is pointed at the object, you can study it more closely through the main scope.

Electronics - Many telescopes come with electronic features that you might find useful. Make sure to check and see if there's RS232 port for communication with your computer, camera control and auxiliary ports or a camera shutter release cable if you plan to photograph the objects you're studying. Computerized telescopes often have hand controls for easily navigating the system; be sure to look and see if this is a feature you'd like to take advantage of.

Software - Celestron telescopes often include software to help you learn about the objects in the universe and the basics of astronomy. For even more information, you can purchase expansion cards to broaden your telescope's computer database.

Click here to browse our telescope collection and make a purchase.

If you have questions about which scope is right for you, or prefer to shop by phone, give our friendly sales team a call at 1-800-260-2776; we're happy to answer questions, give you a price quote or take your order.

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