Binoculars are an excellent choice for hikers, hunters, birdwatchers or astronomers, but they have two major drawbacks: they are often limited to a maximum magnification of 20x and a lens size of around 70 mm. But what if you need more powerful instruments?

That's where spotting scopes come in. A spotting scope is precisely designed to be both portable and powerful, two assets particularly sought-after by outdoor enthusiasts. But what should you look out for when choosing your spotting scopes? How do you choose the model best suited to your situation?

What do the numbers mean?

As with binoculars, there are two factors to consider when choosing a spotting scope: magnification and lens diameter. In both cases, the first number corresponds to the magnification and the second to the size of the lens, measured in millimetres.

For example, 10×50 binoculars have a magnification of 10x and an objective diameter of 50 mm. There is, however, an important difference between binocular and spotting scope magnification: in the case of binoculars, the magnification is fixed, whereas in the case of spotting scopes, it can vary.

There are exceptions, of course. Some binoculars use zoom magnification, but their quality is generally inferior.

When it comes to spotting scopes, you can get an indication like this: 20-60×80. This means that the magnification of this telescope can vary between 20x and 60x and that it has an objective diameter of 80 mm.

The magnification refers, of course, to the size of your target as seen through the spotting scope. Objective diameter refers to the diameter of the large lens that points at your target. The larger its diameter, the more light it can gather. This can be a very important factor if you want to use the spotting scope in low-light conditions (e.g. at dusk).

Why use a spotting scope?

Telescopes offer a number of advantages over binoculars. First of all, spotting scopes offer higher magnification, whereas fixed-magnification binoculars often offer a maximum magnification of around 20x. This same figure will be the minimum measurement for many spotting scopes.

Secondly, spotting scopes have a larger objective diameter, whereas many binoculars have an objective diameter of 70 mm or less. The diameter of spotting scopes varies between 60 mm and 90 mm.

At this point, you may be thinking that a spotting scope is essentially a telescope, and you'd be right. However, there are a few differences in size. First of all, modern telescopes aren't designed to be hand-held, and most are made to be used in a fixed location, so they're attached to tripods or other supports, and while some are more mobile than others, most aren't really suited to outdoor activities like hiking.

Another essential difference: a good-quality telescope can invert the view. The image can be inverted horizontally, vertically or both. If you're interested in astronomy, no problem. But if you're a hunter or birder, this can be a serious problem!

Here's why it happens: the lenses and/or mirrors of a telescope rotate the image as the light moves along its length. An additional lens or mirror is required to rectify the image orientation, resulting in a slight loss of image quality.

This is something to consider, particularly for astronomy, but not so much for other activities. In astronomy, this difference in quality can make it difficult to separate nearby double stars, or to observe the finer details of nebulae, galaxies and other deep-sky objects.

For this reason, dedicated astronomical telescopes generally avoid the need for an additional lens, although the image may be reversed. If you wish to use the same telescope for a daytime activity such as birdwatching, you can buy an accessory that will correct the orientation, but we recommend that you buy a telescope adapted to what you wish to observe.

Finally, an astronomical telescope is designed to produce a high-magnification image, as it is sometimes necessary to have a magnification of over 150 x to obtain the desired image quality of an object. What's more, the eyepieces on a telescope can be interchanged to provide different magnifications. A spotting scope, on the other hand, has just one fixed eyepiece, which can be used to provide a variety of lower magnifications.

Since higher magnification is generally not necessary for an activity such as birdwatching, the magnification provided by a spotting scope, even if lower, is more than sufficient.

In short, an astronomical telescope is designed to be installed in a fixed location, produces an inverted or reversed image and is capable of offering very high magnification. In the case of spotting scopes, the opposite is almost always true. Hikers, campers, birdwatchers and hunters can take their spotting scopes with them wherever they go, enjoying views that are correctly oriented and more suited to their needs, even if the magnification is lower.

How to choose the best spotting scopes?

There are a number of factors you need to consider when buying spotting scopes. Here are the key factors:

• Straight VS Angled
• Lens magnification and diameter
• Weight

Straight or angled spotting scopes?

There are essentially two types of spotting scopes: angled and straight. A bent spotting scope is curved at one end to allow the eyepiece to be tilted upwards, whereas the eyepiece of a straight spotting scope is directly aligned with the spotting scope.

An angled spotting scope offers a more comfortable viewing experience in most situations, although this really depends on your specific needs. If you're standing upright and your target is much higher or lower than you, an angled spotting scope is certainly the best choice.

Birdwatchers, hikers and astronomers, for example, will find it easier to use an angled spotting scope, as the scope can be turned so that the eyepiece is in a more comfortable position for the observer.

A straight spotting scope can be problematic for activities such as astronomy, as the observer often has to twist under the eyepiece to be able to look through it.

Straight spotting scopes are better suited to situations requiring you to lie on the ground for an extended period of time. In this case, looking directly into the telescope will be more comfortable, rather than having to look down through an eyepiece that could be positioned at a 45-degree angle to the telescope itself.

One of the advantages of straight spotters is that you can hold them at eye level, like a traditional hand-held telescope. This allows you to observe objects at any angle above or below you. However, you'll find that the view can be a little unstable if you don't use a tripod.

Magnification and lens diameter

As with straight or angled scopes, the choice of magnification and lens diameter depends on your intended use.

Magnification really depends on how far away you expect your target to be and/or how big it is. Generally speaking, most users will find that variable magnification models are more suitable, as they allow you to see targets that are both close and/or large and further away and/or smaller.

The only possible exception is astronomy. Indeed, a spotting scope can be used to help observers locate a target they would like to observe from a larger telescope, but otherwise many spotting scopes only offer the magnification or lens diameter needed for occasional observation of brighter, larger targets.

As far as lens size is concerned, if you want to use your spotting scope at sunrise, during the night or for occasional stargazing, you'll need a lens with a sufficiently large diameter. Under these conditions, you'll need an instrument capable of gathering as much light as possible, hence the importance of choosing a fairly large lens, which will capture more light.

Weight

Spotting scopes are generally designed to be compact and portable, which is why most of them are quite light. On average, they weigh around 1.9 kg, i.e. 2x more than a pair of 10×50 Porro prism binoculars, but less than the average weight of most astronomical telescopes with similar lenses. Their weight can therefore make them difficult to use over time. They do, however, meet all the needs of hikers, campers and hunters looking for lightweight tools to take with them.

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