By Shari Phiel
Seems like astronomy and stargazing have become relatively popular activities in Town these days. Berthoud boasts not one, but two, telescopes open to the public and Berthoud’s own Dr. Andrea Schweitzer will coordinate the UNESCO International Year of Astronomy 2009.
With all of this heavenly activity going on, as well as being the perfect Christmas gift, you may be thinking of buying your own telescope to get in on the action. A few years back I got a telescope at Christmas but hadn’t really researched what I needed and ended up with the wrong telescope for me. Here are a few things to consider before making your purchase.
Most consumer purchased telescopes fall into one of two categories; refractors or reflectors. Each has its advantages and, of course, each has its disadvantages.
Refracting telescopes bend the light as it passes from one medium (like air) to another (such as glass or a mirror). According to www.astronomy.com, “A refracting telescope makes use of this property with a carefully made lens having curved surfaces. As light passes from air to glass and then back to air, its path is bent toward the optical axis of the lens.”
Refracting telescopes benefit from having a totally clear aperture, meaning light won’t be scattered from brighter to darker areas from a central obstruction found in other types of telescope. Astronomy.com noted, “Refractors often are cited as the premier instruments for planetary and double star observing.”
This kind of telescope is also low maintenance. Refracting telescope lenses do not need to be recoated as mirrors often do. Also, the lens is fixed to the optical tube assembly, generally eliminating the need for collimation (alignment).
But refracting telescopes do have their drawbacks. High-quality refracting telescopes are often very expensive and beyond the price range for many astronomy enthusiasts. The use of lighter materials like aluminum has brought the price down quite a bit, but beware of lesser quality telescopes if you’re just looking to save money. Prices can range from $100 to $1,500 or more.
The other type of commonly used telescope is the reflecting telescope. The first working reflecting telescope was invented by the famous English mathematician and scientist Sir Isaac Newton. In fact, many of the reflecting telescopes on the market today and called Newtonian telescopes.
Reflecting telescopes use two mirrors – a large primary mirror at the bottom of the tube assembly and a smaller, flat, secondary mirror near the top. Light enters the open tube, hits the mirror and is reflected to the secondary mirror and is then reflected a third time to the eyepiece. Because the mirrors used in reflecting telescopes have only one side, as compared to between four and eight in other telescopes, and are much less expensive to manufacturer.
The primary drawback of reflecting telescopes is the scattering of light and loss of contrast due to its construction. Mirrors may also need recoating after several years of use. Reflecting telescopes are also more sensitive to being moved around.
Before buying a telescope consider how you will use it. Will it be permanently affixed to an outside structure or will you be carrying it with you when camping or hiking? How visible are the stars from your home? How much money do you want to spend? Don’t forget about additional expenses like extra lenses or having mirrors recoated.
For more information about buying a telescope, check online at www.astronomy.com. Another excellent Web site is www.space.com. With so much local talent, you can also ask an expert at the Little Thompson Observatory or perhaps even you neighbor. You never know who may be a secret stargazer.