In The Market For A Spotting Scope

It's Good To Know Some Terminology

There are a wide variety of spotting scopes available, especially since many riflescope manufactures also build spotting scopes to compliment their product line. Used primarily to view distant objects or wildlife on the ground, most spotting scopes work like small telescopes with a refractor or catadioptric optical design. Normally, spotting scopes have a 50mm to 80mm objective lens and magnification from 15x to 60x. Of course, there are more powerful scopes with higher magnification and larger objective lenses going to 90mm and up. In this article, we'll explain some of the terminology used when talking about spotting scopes, so you will be able to shop for what you want with a little more knowledge.

The Different Types of Coating For Optics

Spotting scopes have coated optics to reduce light loss and glare due to reflection. This provides for a brighter, higher-contrast image with reduced eyestrain. The coating used on many spotting scopes is a microscopic film of magnesium fluoride and the more coating there is, the better the light transmission. There are different types of coating for spotting scopes which we will define here. Coated spotting scopes means there is a single layer on at least one lens. When the scope is fully-coated, all air-to-glass surfaces have a single layer of coating on them. Multi-coated spotting scopes have multiple layers on at least one lens and all surfaces are coated at least once. A full multi-coated spotting scope has multiple layers on all air-to-glass surfaces.

What's An Exit Pupil?

The size of the column of light that exits a spotting scope is called the exit pupil. The larger the exit pupil, the brighter the image. The higher the magnification on the scope, the smaller the exit pupil will be. This means the image you will see through your scope will be dimmer. To determine the size of the exit pupil; divide the objective lens diameter by the power. For example, a 15x45 model has an exit pupil, or useable light, of 3mm.

Reducing Eye Strain and Seeing More, All At The Same Time

Eye relief is the distance a spotting scope can be held away from the eye while still presenting a full field of view. Having extended or long eye relief will help to reduce eyestrain, making it ideal for eyeglass wearers. Speaking of field of view, on a spotting scope it is the side-to-side measurement of the circular field of view or subject area. The field of view is defined by the width in feet or meters of the area visible at 1000 yards. A wide field of view is better suited for hunters wanting to keep track of quick-moving action or scanning for wildlife. In general, it is important to note, the higher the magnification of the scope, the narrower the field of view.

You Just Might Need A Tripod For That Scope

Size, weight, and mounting, while not optical characteristics of a spotting scope, do figure into the equation when you have to carry your scope across the countryside to get a look at a bird or animal. You'll appreciate something light weight and compact for such things. On the other hand, buying a tripod might be the answer for high power observations of optical magnification 12x and up.