What To Look For
Every pair of binoculars has two numbers on display, such as 7x35. The first number pertains to magnification. Astronomy magazine's website recommends a magnification between 7 and 10 for hand-held use. The second number refers to the diameter of the front lens, or aperture, which affects the brightness of the images viewed through the binoculars. Look for big lenses that let it lots of light. An aperture of at least 40 is required for clear astronomical viewing.
Common Pitfalls
Failing to consider the exit pupil of a pair of binoculars can result in dim, disappointing imaging. The ideal exit pupil, or the size of the light beam exiting the eyepiece, varies according to each star gazer's age. The pupils of people younger than age 30 tend to dilate to approximately 7mm, while those of most people older than 40 only dilate to 5mm, according to Astronomy. Match the binoculars' exit pupil to your pupil dilation for optimal bright imaging. To find the exit pupil of the binoculars, divide the aperture number by the magnification number. For instance, 7x35 binoculars have an exit pupil of 5mm, making them ideal for people older than 40.
Where To Buy
Several Internet stores sell quality astronomical binoculars, such as AstronomyBinoculars.com. The site has the widest selection of brands and sizes, but by purchasing online, shoppers forfeit the luxury of feeling and testing the binoculars before paying. If you want the assurance of a well-built product, Nikon and Canon sell binoculars whose brand names guarantee quality. Best Buy also has a fair selection of binoculars, including Nikon. Call ahead to make sure your local outlet sells them.
Cost
Casual star gazers can find bargains less than $100 on websites, such as AstronomyBinoculars.com. For high-quality binoculars, expect to pay $150 to $250. Some of the best binoculars, such as the Nikon 12x50 Superior E binocular, cost $700-800. If you want large binoculars for viewing on a tripod--meaning those with apertures greater than 50mm--high-end models tend to be $1,000 to $5,000, depending on the brand.
Comparison Shopping
Two types of binoculars are available, the straight, lightweight roof-prism binoculars and the asymmetrical Porro-prism binoculars. The most common binoculars for astronomical viewing are Porro prisms, according to Sky and Telescope magazine's website. They are more user-friendly. Meanwhile, roof prisms are smaller, making them more comfortable to pack. They tend to be poor quality, inexpensive models or high-quality models with hefty price tags, leaving few choices in between.
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