How to choose a spotting scope for birding

The use of a spotting scope is a great way to advance your birding skills. Wonderful for long distance birding, spotting scopes also bring out tiny details that you never noticed previously.

Before you can get out into the field and use the spotting scope for bird watching, you want to be sure that you know how to choose the right one. If you are wondering what to look for in a birding spotting scope you are in the right place. We’ll help you with all your questions about spotting scopes so you can find out which is best for you.

There are many variables to consider, such as magnification power and lens size. What magnification spotting scope do you need for birding? How do you know what size to buy?

Our guide will help break down what makes a good birding scope and which features matter most so you can make an informed decision.

Bird watching with a spotting scope: what do the numbers mean?

You’ll notice that each spotting scope, as well as having a name of its model, also has a pair of numbers in its description.

The first number indicates what power of magnification the scope has – for example 15x or 50x. Scope magnification can also be known as the zoom, or the ‘power’ of the lens. You will see this written somewhere on the body of the scope.

The lens responsible for the magnification is the ocular lens – the smaller one closest to your eye.

The second number tells us the size of the objective lens. The objective lens is the larger lens, located at the end of the binocular furthest from the viewer.

But what is the point of knowing these numbers? Let’s look at how the measurements affect your viewing experience.

How magnification is written

The magnification is indicated in numbers. These show how many times larger the view of a bird appears through the lens rather than seen only with the naked eye.

So a spotting scope that magnifies an image twenty times would be classified as ’20x’, fifty times = 50x, and so on.

In practical terms, this means if you were using a 20x scope to look at a bird 200 feet away, you’d be able to view it as if from a distance of 10 feet.

If you were using a 50x scope to look at the same bird 200 feet away you’d see its detailed markings as if from only 4 feet away.

What magnification is best for a bird watching spotting scope?

Spotting scopes for bird watching usually have a magnification power from 15x to 60x. On many models, the eyepieces can be changed over. This means that you can switch between fixed-power and zoom lenses.

For a fixed magnification eyepiece, 20x to 30x is suitable. This is a good size for general birding use and fits most requirements as it gives the best balance between field of view and brightness.

A magnification power of 20x or 22x is ideal for most bird watchers using a fixed eyepiece.

Interchangeable eyepieces

Many manufacturers offer spotting scopes with interchangeable eyepieces which make it possible to alter the magnification. Some companies produce eyepieces that only fit their own spotting scopes. On the other hand, some brands make eyepieces that can also be used on scopes made by other manufacturers.

With the basic size in the range of 20x to 30x in your kit, it is always possible to add a stronger power, such as 40x. The most advisable way to approach an increase in power is to consider the large magnification eyepiece as an alternative piece of kit rather than a replacement.

In this way it is still easy to locate birds initially using the smaller eyepiece, and then switch to the more powerful one when locked onto a bird that warrants a closer view. Many have a simple bayonet style attachment.

These high magnification eyepieces are well suited to long-distance birding, especially on stationary birds. You’re likely to see the best results in strong daylight.

Variable zoom magnification range on a spotting scope

An alternative to a fixed-power eyepiece is a zoom eyepiece. Zoom eyepieces offer a range of magnifications and allow you to switch between different magnifications easily.

Most popular combinations of zoom eyepieces start from 20x or 25x at the minimum, to 50x or 60x at the maximum. You will see the variable-zoom magnifications expressed like this: 20-40x, 20-60x, 25-50x.

So in conjunction with the size of the objective lens, the numbers are written like this: 15-45×60 and 20-60×80. Both of these are popular sizes of birding.

A zoom eyepiece increases versatility. But it is important to buy the best that you can afford for optimal light-gathering capabilities even at the higher magnifications.

Should I get a fixed or zoom eyepiece for my spotting scope?

Is more magnification better for bird watching scopes?

Part of the joy of bird watching is observing the intricate details and markings of birds, and witnessing up close their subtle behaviours.

It might at first seem logical to get the biggest magnification you can, to see finer details. Some of those birds can be pretty small, after all.

But before you opt for the most high-powered spotting scope you can find, it’s important to understand that a larger magnification can actually make seeing a bird more difficult.

Is a high-powered spotting scope better for birding?

Lenses that are much wider than 40x suffer more from the loss of light and the ambient interference that can distort a view at this magnification. Air currents, dust particles, and heat waves may blur what you see when you look through your scope.

For this reason, magnifications in excess of 40x work best with really top quality glass components. Better glass minimizes these atmospheric distortions.

Spotting scopes: objective lens size

The point of the objective lens is to let the light into the spotting scope. Simply put, the bigger it is, the more light comes into the tube. The more light, the clearer the image.

The size of the objective lens is measured in millimeters. This size is denoted by the second number in the specification of the scope (though it doesn’t specifically mention millimeters).

What is a good objective lens diameter for a bird watching spotting scope?

An objective lens diameter more than 60mm is big enough to give you a bright image in high resolution, without being too large. A lens too big would give a shaky, unstable view.

For digiscoping it’s best to go larger than 60mm. At least 85mm will gather enough light for your camera or phone.

For birding in low light, large objective lenses gather more light so look at a 75mm diameter. An eyepiece of 20x to 30x is a good combination with this size objective lens.

A larger objective lens diameter adds a little weight too.

Zoom eyepieces for birding spotting scopes

Zoom eyepieces could also suit objective lenses of 75 mm. The zoom eyepiece is a good option if much of your birding is conducted from a fixed spot, such as a hide.

The best combination of objective lens to use with a zoom eyepiece is one that gathers enough light to ensure a bright image. Higher magnification eyepieces tend to limit how much light is transmitted to the eye and therefore reduce the brightness and clarity.

Larger objective lenses, such as 80mm, allow lots of light in. This is good news for birders who want a spotting scope that copes well in lower light conditions.

Do I need a spotting scope for bird watching in low light conditions?

Birds are more active around sunrise and sunset. Consequently, these are the best times of the day for bird watching.

In many cases, if you are bird watching early in the morning or in the evening, you will do better to choose a spotting scope that offers bright images despite low light conditions. This means getting an accurate color reproduction in sharp focus at all times of the day and in different weather conditions.

You want a scope with excellent light transmission to give a consistent image clarity. A sharp image and accuracy of color even in low light increases your enjoyment of the finer details. In some cases it can also be crucial for identifying the bird itself. The size of the exit pupil is also an important factor.

Exit pupil on a spotting scope

A wider exit pupil delivers a brighter image. Because a bigger exit pupil has a greater capacity to gather light and deliver it to your eye, the image will be brighter.

This is true – but only up to the limit of the maximum diameter of the eye’s pupil, which is around 4mm to 7mm. This diameter varies, depending on your age and the amount of light available.

For most bird watching, in average light conditions, a spotting scope with an exit pupil size in excess of 1.33mm should be sufficient. This measurement is determined by the size of the objective lens in relation to the magnification.

To calculate exit pupil, divide the diameter of the objective by the power/magnification.

Image quality

As the magnification of the spotting scopes increases, so too does the importance of having high quality glass components, namely the lenses and prisms. It is worth knowing about the available upgrade in the glass itself and the coatings applied to it.

Types of glass

You will often see these referred to:

• ED – extra-low dispersion
• FL – Fluorite
• HD – high density or definition
• APO – apochromatic

Let’s explore these more closely.

Extra low dispersion (ED) glass

Due to their rounded shape, lenses can suffer from a distortion that affects the image reaching your eyes. The best birding spotting scopes incorporate extra low dispersion glass (ED glass).

The enhanced way that ED glass directs the wavelength of the light to your eye ensures more brightness and clarity. It also gives a more accurate rendition of the color spectrum.

Your perception of color is also improved by the prevention of chromatic aberration. Chromatic aberration is when you see a kind of rainbow effect at the edge of objects.

FL and APO glass

Specifications may also refer to FL glass. This stands for fluoride, which is another high grade of glass used in optical instruments to reduce chromatic aberration.

Other types of glass used to minimize chromatic aberration referred to in spotting scope specifications are achromatic glass and apochromatic glass.

HD glass

Sometimes the fact that an optical instrument benefits from ED glass leads to it being described as high definition. ‘High definition’ is, in the case of birding optics, not a defined term. So when you see it used, it is best to clarify exactly what it refers to in that description.

Overall, ED glass elements will minimize aberration and distortion. This has the consequence of improving image sharpness and color quality. A higher grade of glass means a higher standard of viewing experience.

What is ED (extra low dispersion) glass in bird watching binoculars?

Lens coatings for spotting scopes

Fully multi coated optics will improve image quality. They do this by reducing reflection and assisting the transmission of light through the objective lens. In short, an anti-reflection multi coated lens is worth paying for. This is because it produces a brighter, clearer image.

The reduction of reflection and improved light transmission by effective lens coatings will even allow a birding scope of a lower magnification to compare favourably with an uncoated scope of the same magnification.

Why are prism and lens coatings important to birding binoculars?

Eye relief on spotting scopes

Eye relief distance refers to the gap between the ocular lens (the glass closest to your eye) and your eye itself. It is an especially important measurement for people who use glasses.

In this case, you will need a greater eye relief as your eye will be a bit further from the ocular lens. It’s important to get this right to preserve the width of your field of view.

If you don’t wear eyeglasses, look for a measurement of 9-13mm. This will allow your eye to be at the right distance for a nice wide field of view.

What eye relief do glasses wearers need on spotting scopes?

A comfortable measurement for wearers of thinner glasses is an eye relief between 14-15mm. For those who wear thicker glasses or those that don’t fit as closely to the face, choose an eye relief of 16-18mm.

Many models have adjustable eye cups. These eye cups can be twisted out to extend the eye relief for people who do not use glasses.

As well as allowing you to adjust your eye relief, eye cups also help shade your eyes from any extra distance while you are viewing.

Some scopes may feature a rubber eye cup that can be folded back to allow your eye to be as close as possible to the lens. In this way, the field of view can still be as wide as possible.

Using a spotting scope with glasses: how much eye relief do I need?

Spotting scopes: ease of focus

There are three main designs of focusing mechanisms on spotting scopes: single knob, double knob, collar (or helical).

With the helical or collar style, the body of the scope rotates. Usually the barrel has a rubber coating or ridged surface to make it easy to grip as you turn it. This design is quick and easy to use.

Alternatively, you will find a focusing knob on top of the scope. This design can be more fiddly to use, especially with thick gloves. The advantage is that it is better for really fine tuning of the focus.

Some manufacturers offer double knobs to focus. One of them can be used for rapid focus to get you roughly in the correct vicinity. Then, the other allows you to make fine adjustments from this point.

Spotting scopes: field of view

The term ‘field of view’ refers to the width of the area visible through the spotting scope. Why is a good field of view important in birding?

Try to select birding optics with as wide a field of view as possible because you’ll be able to scan a larger area of landscape. This will help you to find the bird in the first place.

Plus if it flies away, a wider field of view also allows you to follow it more easily. You’ll feel like you are able to take in a whole panorama, not be limited to a small area of sky.

Conversely, while a narrow field of view would give a better image of a stationary bird, it would also make it less easy to track the bird in flight.

Field of view: what do the numbers mean?

Given that a larger value indicates a wider field of view, exactly what specification are you looking for when determining which field of view is best for your requirements?

Spotting scope specifications present the field of view in this format:
400ft at 1,000yd
What the numbers actually tell you is the width of the scene that you can see at 1000 yards. This is expressed in feet at 1000 yards.
These specifications may also quote the field of view as an angle, in degrees: 6.5°

What field of view is best for a bird watching spotting scope?

You’ll be looking for the field of view to be at least 390ft/1000 yards.
This would mean that the angle seen from your scope is 7-8 degrees.
While this doesn’t sound like much, remember that the angle widens right out the further it goes away from you.

How do you calculate field of view for birding?

Each additional degree on your field of view adds roughly another 50 feet of width to what you can see a distance of 1000 yards away from you.

It’s important to pay attention to the number indicating the field of view because it can vary even between models that otherwise seem to have a very similar spec.

The wider field of view offered by a fixed wide-angle eyepiece will enhance your viewing in birding locations where there is a lot of open space, such as seascapes or ridgelines.

Comparing a fixed magnification eyepiece with a zoom eyepiece with the equivalent magnification, you may notice that the fixed one has a wider field of view.

Spotting scopes: close focus distance

Like field of view, close focus distance describes how much of the landscape you can see through your scope. The measurement tells you how close you can be to an object while still able to focus on it clearly.

Typically, as magnification increases, the minimum close focus distance also increases.

The best close focus distance for a birding scope

Though most people purchase birding optics for an enhanced view of distant things, there may be times when you would like a detailed look at something that is only a few yards away. Some scopes that are not specifically made for birding cannot focus on an object that is nearby.

What you are looking for in a bird watching scope is a close focus distance of around 15 to 20 feet. The close focus distance of a spotting scope is usually longer than a pair of binoculars, which can be just six feet.

While you are out looking for birds, other creatures are sure to cross your path. So, being able to quickly focus on a butterfly or small mammal is a bonus. A shorter close focus distance is also more suited to digiscoping.

How to choose a spotting scope for digiscoping

If you want to do a lot of digiscoping, you’ll want your scope to deliver the brightest image possible to your camera. Look for an objective lens around 85 mm.

A good combination to use for digiscoping is a lower magnification eyepiece with a larger objective lens. The larger the objective lens and the lower the power of the eyepiece, the more light that is transmitted to the camera attached to the eyepiece.

Larger objective lens + lower magnification eyepiece = brighter image

Whatever combination of sizes you choose for your digiscoping, the use of a sturdy tripod reduces the risk of image shake.

Spotting scopes: optical design

Straight spotting scope or angled scope?

One of the most debated elements of the optical design is whether to choose an angled spotting scope or a straight spotting scope.

The difference between these two types of spotting scope is structure. This can be easily seen at the rear of the instrument and indicates how the spotting scope directs the path of light through the body of the instrument.

On straight spotting scopes, the eyepiece and objective lens are aligned with each other and are parallel to the ground. Beginners may find a straight scope more intuitive to use because it is in line with the eyes’ natural viewing angle.

On an angled scope, the adjustable eyepiece is at an angle in relation to the objective lens. The angle usually ranges between 45 to 90 degrees, so the body of an angled spotting scope curves to accommodate this configuration.

Angled scopes have more stability because they are used with a tripod set up at a lower height. Many people consider that they are better for digiscoping.

In general, when it comes to size and weight there is little difference between them. This also goes for other areas in their specifications – like the visibility and price tag. However, there are so many different facets to understand in this subject that we have dedicated an entire article to it.

It is an integral part of your decision when choosing a spotting scope for birds so you can find the detailed article here >>>

Angled vs straight spotting scopes: which is best for birding?

Refractive or catadioptric?

Another important aspect of the optical design to be aware of is whether the scope is refractive or catadioptric. Either one sounds kind of painful. But we can assure you both are quite harmless.

Most birding spotting scopes that you will find on the market are refractive. This is because the refractive design can be manufactured at a lower cost and can be used with either fixed or zoom eyepieces.

In comparison to a catadioptric scope, a refractive spotting scope has a wider field of view. They are more robust and require less maintenance.

Refractive scopes use lenses to bend the light through the barrel of the scope, whereas a catadioptric scope does this with mirrors. A catadioptric scope presents a reversed image. It is the right way up but is flipped round from left to right.

When you want to greatly increase the magnification then the catadioptric scope is able to do this with no loss of quality. With a refractive scope, however, quality starts to deteriorate past 60x.

Weight and size of spotting scopes

Many birders will be outdoors and on the move when they are bird watching. One of the main benefits of birding is getting out for some fresh air and exercise. But keeping the weight of the kit that you carry to a minimum will preserve your freshness and focus for appreciating the scenery and birds, rather than making the outing feel like a weight-training session.

Lens size affects overall dimensions

The size of the lenses has a bearing on the dimensions and weight of your spotting scope.
The objective lens diameter is a valuable indicator of how large and heavy the instrument might feel in your hands and to carry around in your bag or – ready for action! – around your neck. The compromise with 80mm lenses is the unavoidable increase in dimensions and weight.

Waterproof and fog proof spotting scopes

Weather, as well as having an impact on your viewing due to the level of light, can also affect the bird watching scope itself. Fog proof and waterproof, despite sounding like similar features, actually tackle two different issues that birdwatchers might experience.

Fog proof

You need a spotting scope that is fog proof because sudden temperature changes can cause condensation to form on the internal surface of lenses. For example, as you leave your cosy interior to go out into a chillier atmosphere, or as you move from an air-conditioned room into a warmer environment, your spotting scope is at risk from some moisture getting inside them.

This internal fogging can be difficult to get rid of. Clearly this has a negative impact on the image clarity. This is because you are looking through a lens covered with tiny water droplets.

A specific process fog proofs the best spotting scopes for birding. The manufacturer totally seals and fills them with a gas that does not condense when subjected to temperature changes.

You might be looking for the best spotting scope for a foggy environment or somewhere with frequent fog. For example, in the early morning, when bird watching by the coast, in mountainous regions or in tropical cloud forests. Then it is worth researching which binoculars will meet your needs in different circumstances.

Waterproof

It’s best to look for birding spotting scopes that are waterproof, even if you live in a climate where rain or mist is less frequent.

A fully sealed interior not only prevents the moisture that is always present in the air from entering but also protects  your instrument from accidental spillages. So even if you intend to be a fair weather birder, look for bird watching spotting scopes that are waterproof and fog proof.

Choosing a spotting scope for birding – solved!

The wide variety of spotting scopes on the market can make it difficult to choose a spotting scope for birding. We hope these tips on the essential aspects of spotting scopes will help bird watchers know what to look out for.

Once you understand which features matter most to you when picking a spotting scope for bird watching it is easier to narrow down your choices.

Remember to consider whether to choose a straight spotting scope or an angled scope. It is an integral part of your decision when choosing a spotting scope for birds so you can find the detailed article here >>>

Angled vs straight spotting scopes: which is best for birding?