Friday, February 5, 2010

Demystifying Spotting Scopes

Perhaps you’ve looked at a bird through a spotting scope during a field trip and were completely awed by the intimacy of the experience. When it comes to observing a bird, nothing personalizes the experience better than the view through a scope. Intricate feather detail is revealed as a bird raises its crest, preens, or gobbles down a caterpillar. Maybe you’ve witnessed the stoic glare of a Great Horned Owl’s huge irises looking back at you. Spotting scopes also offer the birder the opportunity to watch birds that are often unidentifiable because they’re far away on a body of water like a large lake or ocean. These are some of the offerings that await the birder who hasn’t yet acquired their own spotting scope. For some, there’s a perception that spotting scopes are just plain difficult to use.

Binoculars versus Spotting Scopes

A fundamental difference between a binocular and spotting scope is that you actually wear your binocular and it feels intuitively like an extension of your vision. On the other hand, a spotting scope is discernibly extra. It’s separate, less portable, and because you have to carry it around, your hands aren’t always free to use your binocular. Because spotting scopes offer higher magnification than binoculars, they naturally have a narrower field of view. While this makes aiming and following a subject inherently more difficult, veteran birders say that with practice one can become very adept locating even warblers through a spotting scope. All of the above points will affect your style of birding.

As someone who has been selling spotting scopes for a decade, I occasionally sense first-time scope buyers have a perception that spotting scopes are also more mechanically complex than a binocular. A quick way to dispel this notion is to keep in mind that a spotting scope is essentially just half of a binocular! By examining what’s inside the barrel of a binocular and spotting scope, you can see the same components: There’s an objective lens that gathers light, a prism block, and an eyepiece where the image is brought into focus.

Angled versus Straight

Spotting scopes are usually available in two body styles, straight and angled. This just means how the eyepiece mounts or is fixed to the body of the spotting scope. A straight scope’s eyepiece is merely an extension of the body, while an angled scope’s eyepiece is fixed or installed at a 45 degree angle from the body. Though the majority of spotting scope buyers go with the angled format, the advantages and disadvantages of both types is worth mentioning. The main advantage of the angled design is that it works best when the scope is being shared with a group of people - the tripod center post doesn’t need to be raised or lowered according to the height of the person viewing through it. This advantage is obvious when viewing wildlife, because the subject you’re viewing generally has to be reacquired with each tripod center post adjustment. Another advantage to the angled design is that the scope doesn’t have to be elevated as high on the tripod center post to reach a comfortable viewing height, thus providing greater stability.  Straight-bodied scopes are especially convenient to use when viewing downward from high positions or from confined spaces, such as scanning below a mountain or watching wildlife from a vehicle.

Aperture Size versus Portability

The objective lens size represents the aperture of the spotting scope and serves the function of gathering light. Smaller aperture spotting scopes (60mm, 65mm, etc.) are made for a good reason; they're smaller and lighter in weight. Lugging around a large spotting scope (80mm, 85mm, etc.) and tripod can become burdensome on long hikes, and the nominally lighter weight scopes do seem to make a difference for individuals who suffer from neck or back trouble. As I stated above, larger aperture spotting scopes gather more light, thus they perform better in low light and render greater detail at distances compared to their smaller aperture cousins. Additionally, if you intend to do photography through your spotting scope, the larger aperture scopes will generally provide better results. This is the essential compromise when it comes to aperture - portability versus light gathering. Thus, your decision rests on priority: are you going to place an emphasis on photography, or would carrying a lighter weight spotting scope benefit your outdoor excursions?


Owning a spotting scope doesn’t obligate you to take it out every time you go birding. When I anticipate increased songbird activity during spring migration, sometimes I’ll leave my spotting scope at home and simply enjoy birding with my binoculars. But if the lighting is remarkably good, perhaps I’ll consider the possibility of doing a little digiscoping that particular morning. When observing gulls or shorebirds, a spotting scope is invaluable for making accurate identifications. There’s also nothing like the participant's smiles during a field trip when I aim my spotting scope on an owl's face! It's ultimately up to you, but now you know a few of the trade-offs to make a more informed decision before purchasing a spotting scope.

Mike McDowell
Eagle Optics Staff

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