There is something really magical about being able to see even the tiniest details on birds from dozens of meters away. Because your powerful spotting scope enables you to stay so far away, they are totally undisturbed. With the great images, you can be part of their world and observe their completely natural behaviour.
Let’s say you have already upgraded the magnification of your spotting scope by switching over the eyepiece. But you would still like to get even closer. It is a natural reaction to the wonder of the optical device’s quality.
Alternatively, right now you might be at the very beginning of your bird-watching journey, still considering whether to invest in any kind of birding kit. So it is definitely worth knowing which sorts of products might take the experience even further past your expectations, when you are ready to develop your skills.
Whichever is your current situation, it’s good to know that there is an easy addition that you can make to your scope to increase magnification even further on occasions when you wish to. This is what is called a magnification extender (ME).
They may be a small but easy addition to your kit. But at their price point there are some aspects to consider before making the investment. Let’s take an in-depth view of the finer points of magnification extenders.
What is a magnification extender?
Photographers might be more familiar with these devices being described as tele extenders. For astronomers they are referred to as Barlow lenses. A magnification extender works in the same way as a teleconverter would for an SLR camera.
An ME will typically increase the magnification from between one and a half to two times. This is a major boost to your bird watching power. It really increases the versatility of your spotting scope when used in conjunction with a variable zoom eyepiece.
Find out what else you need to know about scope magnification here >>>
Changing eyepieces on a scope: how to increase magnification
The exact figure will depend on which extender you use, and which spotting scope and eyepiece it is combined with. The magnification extender itself is of a fixed magnification. But it can be used with either fixed or variable magnification eyepieces.
There are only a few manufacturers who make magnification extenders, which are to be used with their own products. In this case, you just fit the extender by screwing it onto the thread of the existing adapter.
Since you would be using the extender in combination with the same brand’s products, the optical quality is matched. This means the quality of the image should be preserved in terms of sharpness, contrast and clarity.
What you need to know about magnification extenders
Brightness may be affected
What might be impacted, though, is the overall brightness. By its very nature, the extender is extending the length of the path that the light has to travel. Despite the best glass and coatings, this longer path of transmission inevitably results in more of the light being lost along the way.
To be exact, the total amount of light transmitted is reduced by the square of the magnification. This is the case for any tele extender. So if you are familiar with the terminology of photography, the reduction in light is equivalent to one and a half f/stops.
In practice, this means that magnification extenders are best added to your spotting scope and eyepiece to be used in bright light conditions. Then the chances of noticing any visible difference is greatly reduced. This is your best way of avoiding registering too dim an image.
Choose the right atmospheric conditions
The high magnification of spotting scopes already makes them more susceptible to atmospheric distortions, such as heat waves. By increasing magnification even further by adding an extender, these air disturbances become even more noticeable.
So, while it’s best to put the extender on the spotting scope for use on a bright day, it is also necessary to consider the weather conditions. If possible, opt for a time or location where light is good but that heat waves do not interfere too much with the clarity of the image.
How should I choose a magnification extender?
Some of the top brands make magnification extenders to be fitted to their own products. These include Kowa, whose 1.6x extender will boost the eyepiece of the TE-11WZ from 25-60x zoom right up to 40-96x. They claim to have created this product with minimal loss of light.
Most of these magnification extenders will be suitable for use with either the straight or the angled spotting scope models. The extenders will often have their own thread, which will allow further adaptors or accessories for digiscoping to be attached as well.
The extender doesn’t need to be a permanent attachment and can be switched on and off without any complicated modifications. In some cases, the design means that the extender fits between the body of the scope and the eyepiece.
Which brands make magnification extenders?
In the case of Kowa’s extender, for example, it can be added easily just by screwing on to the scope body. Once it is on the scope, the eyepiece can be attached using a neat bayonet mount. There is a quick-release button to allow you to take off the eyepiece easily.
Because these tools are made mainly by the top optics manufacturers, the high quality optical components keep the light lost by the extender to a minimum. While the magnification extenders are made mainly by the top-of-the-range brands, this guarantees that you are getting the very best equipment.
The drawback, of course, is that the use of an extender is limited to those who have a product from the brands that make them. Other companies as well as Kowa that produce extenders are Leica and Swarovski. Leica’s extender, at 1.8x, fits the APO-Televid scope body at either 65mm or 82mm.
The total magnification will depend on the size of the scope and eyepiece with which the extender is combined. Here are some examples to see how this works out in real life.
Practical use of magnification extenders
The Swarovski extender is 1.7x. It can be used with the 65mm, 85mm or 95mm models in their ATX (angled), STX (straight) and BTX (binocular) ranges.
For the angled and straight 65mm and 85mm models, the 25-60x zoom range is increased to 42-100x. For the angled and straight 95mm models, the 30-70x zoom range gets a boost to 50-120x.
In the BTX range, which has a fixed magnification, the 30x eyepiece on the 65mm and 85mm models increases to 50x. On the 95mm BTX, the 30x is 60x with the addition of the 1.7x extender.
For the BTX 65mm and 85mm, for example, the magnification would increase at the lower end of the range from 30x to 50x, while the 95mm version moves up from 35x to 60x.
Final thoughts on magnification extenders
An extender provides a significant boost to the magnification power of your existing spotting scope and eyepieces without any hassle. It is suitable for very high powered bird watching for longer periods of time.
To learn more about distances that you can see through a spotting scope, this article may be helpful: Different distances: How far can I see with a spotting scope?
Provided that it is used in the appropriate conditions, an extender can be a great addition to your bird watching kit. There are also options to swap the eyepiece on your spotting scope for a wide angled lens. We cover that here > Is a wide angle lens better for a spotting scope?
For further discussion of different options of eyepieces, check out this article: Changing eyepieces on a scope: how to increase magnification
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