Envision someone with sky-gazing binoculars

Greetings, stargazers. This is the time of year retailers love, and many of you might be in the market for a new gadget to help with your stargazing endeavors.

Thinking of a telescope? By far, the best telescope is the one that gets used the most.

But if you ask me what kind of telescope is the best one to get, I will likely ask you what kind of binoculars you have. Binoculars are great in their versatility, portability and affordability. And for the price of a truly entry-level telescope, you can get a nice pair of binoculars that should last a lifetime.

Binoculars are identified with a pair of numbers that represent the magnification and diameter of the front lens. For example, 10x50 binoculars will magnify a factor of 10, and the diameter of the front lens is 50 millimeters (about 2 inches). Ultraportable bird-watching binoculars might be 7x20, and you might find giant 20x100 binoculars mounted on a permanent pier at a national park scenic overlook. Because the pupils of young, healthy eyes are about 7 mm in diameter, astronomers jokingly refer to naked eyes as 1x7 binoculars.

For stargazing, 10x50 is the size I most often recommend. It falls in that goldilocks range of not too small and not too big. Since light-gathering ability is the only thing that matters for stargazing (that goes for telescopes too), the bigger the lens, the better the view. The 10x50 binoculars gather about 50 times as much light, so you can see things that are 50 times dimmer. To get the same factor increase in light gathering over 50 mm binoculars, you would need to get a 14-inch diameter telescope.

Tripods really do improve the view, but I am promoting ease of use and portability. Binoculars bigger than 50 mm are too heavy to hold steady for any length of time. Similarly, magnifications greater than 10 will give you a shaky view.

Shopping for binoculars can be like many other things Ė there are bargains and lemons. But for a wide price range you get what you pay for. My opinion is that almost any pair of binoculars will give you an improved view of the sky, but there are some things that you might find worthwhile to pay extra for.

The most useful extra for night viewing is anti-reflective coatings. All binoculars have numerous air-to-glass transitions, where reflections will happen, and your image gets worse at each surface. If you wear glasses, you may know anti-reflective coatings make more of a difference in cutting down glare at night, and this is especially true when stargazing. More expensive binoculars tend to have more surfaces coated with better coatings.

Another thing to consider is what is called eye relief. That is how far from the lens your eye needs to be to see the full image. Lower-cost binoculars generally have short eye relief. If you wear glasses, or even sunglasses during daytime use, you might consider binoculars made with extra long eye relief so you donít need to remove your other eyewear to use them.

Image stabilization and weatherproofing are more options you could consider.

This month

Look to the east right after sunset for several great binocular targets. Jupiter is the brightest object in that direction. With binoculars you should be able to see the four Galilean moons, possibly even better than Galileo did.

The Pleiades, or seven sisters, are a nice naked eye cluster, but they are an outstanding sight in binoculars.

A little later in the evening, look for Orion and other winter constellations to make their return. The three belt stars of Orion are right along the celestial equator, so they will be due east when they rise soon after 9 p.m. Bright red Betelgeuse and much bluer Rigel are positioned symmetrically to the left and right of the belt when Orion crosses the horizon. As the night progresses, Orion becomes more upright.

The Orion nebula is the brightest star-forming region that we can see, and is one of the most rewarding targets in binoculars.

hakes_c@fortlewis.edu. Charles Hakes is an assistant professor in the physics and engineering department at Fort Lewis College and is director of the Fort Lewis Observatory.

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