Binoculars – The Perfect Observing Aid

Watching the night sky roll overhead is a fundamental experience that everyone should have an opportunity to share. It lets us temporarily set aside our daily routine and pace ourselves with the universe. Learning the locations of the constellations can help us feel a sense of place in the cosmos and can be thrilling and calming at the same time.

Of course we understand that when getting started in astronomy one of the really fun things to do is learn about the equipment, and that most often means telescopes. Learning about the different telescope construction types, reading various buying guides, studying specifications, even learning the basic mathematical formulas for the optics absolutely can be a ton of fun. But without the ability to navigate ones way around the sky it can be deceptively difficult to locate specific objects with a telescope. Even modern Go-To systems that will locate and frame objects in the eyepiece for you are not a substitute for learning the sky. Gazing at semi-anonymous objects located I-don’t-know-where looses is allure quickly. Unfortunately many beginners jump right in with a new telescope and after a few nights of looking at the moon, a few planets, and randomly sweeping the sky, pack their scope away and rarely take it out again.

The sky on a dark night is impressive to even the unaided eye. With a simple pair of binoculars you can explore the heavens to a far deeper extent than you may realize. You will suddenly be treated to stars and deep sky objects that you cannot even see with the naked eye. There are approximately 3,000 naked eye stars; of course that number depends on observing from a very dark location. With 35mm binoculars you will suddenly have close to 100,000 objects that you can view from that same very dark location. And when we say simple, we do mean a simple pair of binoculars. The same pair of 7×35 or 7×50 binoculars you may have in the back of a closet or stored in the basement will do quite well (actually even better than hyper-gigantic “Astronomy” binoculars).

Binoculars have several important advantages over the typical “astronomical” telescope, particularly for the beginner.

To start with, the primary goal of both telescopes and binoculars is to gather more light than our naked eyes can. (Binoculars are actually just two compact refractor telescopes side by side.) The ability of either to collect light is directly related to the diameter of their objective lens (or mirror). A pair of 50mm binoculars has twice the objective lens area of a 50mm telescope. This advantage combined with lower power magnification can make images in binoculars appear much brighter than in similar sized telescopes. Certain star clusters, nebulae, and comets may actually be seen better in binoculars than in any other optical instrument.  The star clouds and dust lanes in the Milky Way will appear rich and vibrant in binoculars, especially when compared to the sterile and isolated image through a telescope eyepiece.

Compared to a telescope, simple binoculars will give you a much wider field of view (FOV). A typical small to medium telescope will give you a field of view of 1° or an area of a little more than 3 square degrees. Instead of seeing constellations you will see individual stars, divorced from their surroundings and context. Most small to medium binoculars give you a FOV of 6-8° which is about 25 square degrees. Most constellations will still not fit entirely in the eyepieces at one time but you often will be able to see several stars at once.

This brings us to another very important point, navigating the sky through the eyepiece. In a telescope the view in the eyepiece will be upside down, backwards, or both! This makes moving the field of view around very counter-intuitive. Learning to push the scope right to move the objects in the eyepiece left (or up to move down) can absolutely confound the process of learning the relative positions of stars and constellations. There is no reason a beginner has to go through this dual learning curve; binoculars produce images that are straight on and right side up. Moving your gaze left, right, up, or down is as natural as it sounds. This makes it much easier to learn what is just west or directly south of something else. You may have read in your favorite atlas that an easy way to find Arcturus and Spica is to follow the curve of the handle of the Big Dipper. This is not something that is easily accomplished while looking through the eyepiece of a telescope with a 1° FOV but can be done quite naturally while looking through binoculars.

There is another dimension to the dual learning curve, and that is simply learning to use your telescope in the first place. To properly set up a telescope you may need to: align the mount (if you have an equatorial mount), collimate the optics, align the spotting scope, and select an appropriate eyepiece. But in addition to this, if you are not observing from a deck right outside your home you can add transporting and carrying all this equipment out to your observing location. Binoculars are easy to understand and have few adjustments necessary to get up and running (by few we pretty much mean ONE) so your attention can be focused on what you want to look at, rather than on the tool you are using. In addition, they can be carried around your neck, stored in a glove box (with your planisphere), and are ready to go in seconds.

Did you catch that part about setting up your telescope? You may have noticed that bit about mounts, spotting scopes, collimating, and eyepieces. Mass production has drastically reduced the cost of telescopes and many beginning astronomers may consider the cost of entry and mid-level models to be quite affordable. Keep in mind that there will be considerable additional expense for “support” equipment. When you add up the cost of a carrying case, tools for collimating the optics, filters, eyepieces, dew heaters, a Telrad, a chair or step stool, a battery system (if you have Go-To drives), etc. you will quickly double or triple what you spent on the telescope. All of this is good stuff, but considering the real investment it is better to have some personal observing experience to guide your selections. (Heck, you might even be able to rationalize splurging on even better equipment once you have some first-hand knowledge.)

In closing we would also like to point out that you will use binoculars your whole astronomy career, they are not the badge of a greenhorn. Take a close look at the equipment of the old timers at a star party. In addition to some pretty impressive telescopes, cases of eyepieces, and stacks of charts they almost always have a pair of binoculars nearby. As we stated above, binoculars provide you with a wider field of view and a better sense of context. They are good for “zeroing in” on the neighborhood of objects you intend to observe with your telescope to evaluate the “seeing” conditions. Finally, as we stated above some larger objects just look better in binoculars. The Andromeda Galaxy, for instance, is about five times as large in the sky as the full moon. It is not commonly noticed because it is faint; binoculars show it beautifully.


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