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Personal Technology: Seeing Stars

Harvey Laney

For anyone who has considered adding astronomy to his or her list of hobbies, now is as good a time as ever to take the first step. Late this summer, Mars will pass closer to Earth than at any time during the past 73,000 years, but even this rare event will not match the nightly spectacles provided by Jupiter and Saturn, both of which are visible until at least June.

The first step is deciding what type of telescope best fits your needs. If your primary interest is in viewing the planets, moon, and other relatively close objects, consider a refractor—the design that most people think of when they hear the word telescope. A refractor operates by gathering light at one end of the tube assembly and focusing it through a series of lenses to the other end. The larger the lens (called the objective) on the entry end of the tube, the longer the focal length and the better the image that is produced. The lenses of top-of-the line refractors, such as Orion’s Vixen 102-FL ($2,300) and Takahashi’s TOA-130 (about $5,000), contain a new man-made element called fluorite, which helps to produce excellent images with very little color aberration. These scopes are rated "apochromatic" and deliver the truest color possible.

A problem with refractors, however, is that their design limits the size of the aperture, or diameter of the objective. As the aperture increases, so too does the length of the tube, or focal length. This is not a problem with giant refractors built for observatories, but an aperture large enough to gather sufficient light to view deep-space objects would create a tube too unwieldy for a personal telescope. Also, accessories such as a camera mount are necessary if you intend to photograph what you see through a refractor.

On the other hand, many top reflector telescopes, including Orion’s Atlas 8 EQ ($1,100), come equipped with a camera adapter for astrophotography. Even with the best reflectors, though, the human eye cannot clearly view galaxies, planetary nebulae, and other deep-space objects. The camera, however, can gather more light during a long exposure, enabling a photograph to capture images that are impossible to see through the telescope alone. Reflectors are used for deep-space viewing because internal mirrors effectively lengthen the tube, which enables the telescope to collect more light and accommodate larger lenses. Over time, however, the mirrors will require readjustments to maintain the proper focus.

Perhaps the most popular scopes for beginning astronomers, particularly city dwellers and others who want portable scopes to take to areas free of light pollution, are Schmidt-Cassegrains. This type of telescope employs lenses and mirrors, and the result is a very small, portable tube assembly. Because so many amateurs favor this design, some Schmidt-Cassegrain models, such as Celestron’s NexStar 11 GPS ($3,000) and Meade’s LX200GPS ($4,295), include GPS devices. Input your coordinates, and the telescope will find objects to view.

Telescopes at this level are usually sold separately from mounts, eyepieces, and other accessories, but the importance of selecting the highest-quality accoutrements cannot be overstated. For a mount, the rule of thumb is to spend a sum equal to what you paid for the tube assembly. After all, a telescope on a shaky mount is useless.

Celestron, www.celestron.com; Meade, www.meade.com; Orion, www.telescope.com; Takahashi, www.takahashiamerica.com

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