Spotting scopes are available in a wide range of magnification settings. Prospective buyers can find many different models at wild bird stores or nature centers, where they can test various options and compare their features.
The magnification level of a spotting scope limits how much detail you can see. This is because the size of the light beam that reaches your eye—the exit pupil—decreases with higher magnification levels.
Image Quality
Image quality is as essential as magnification when looking at spotting scopes Canada. This is especially true when it comes to close focus.
Regardless of the model or brand, all spotting scopes have a finite amount of light that can enter through their objective lens to illuminate an image. The higher the magnification, the more light is needed to get a crisp, bright image.
This is because the higher the magnification, the more detail you can see, and details tend to contrast more between light and dark areas. This contrast is called chromatic aberration, and it can show up as color fringing on the edges of dark and light parts of an image.
Spotting scopes with special low-dispersion glass typically eliminates chromatic aberration. This makes them a good choice for those who want to use their spotting scope for digiscoping. However, even this can’t eliminate it if you use a high magnification.
Exit Pupil
The size of the spotting scope magnifier’s exit pupil affects how bright your view appears. A larger exit pupil is better for low-light conditions such as dawn and dusk. It also improves contrast on extended objects such as galaxies and nebulas. This is because the brightness of these objects is proportional to their square. Thus, a low-power 4mm exit pupil gives four times as bright a view on these faint fuzzies as a medium-power 2mm exit pupil.
However, if the magnification is more significant than the diameter of the dilated pupil of your eye, then some light is lost. A simple rule of thumb is that the maximum magnification should be at most 60x per inch of aperture in good atmospheric seeing. This prevents magnification diffraction from making a fuzzy blur even larger. The eye pupil also decreases with age, which must be considered. Ideally, a 5mm to 7mm exit pupil is ideal for viewing Milky Way open clusters, large nebulas from dark sky sites, and in mildly light-polluted suburban locations.
Focal Length
Most spotting scopes offer a wide field of view, useful for observing wildlife or following fast-moving action. It is also possible to find models with extended eye relief, which reduces eyestrain for eyeglass wearers.
The larger the objective lens, the more light the spotting scope can gather and the brighter the image. Some high-quality models are available with ED (extra-low dispersion) glass, which produces pure white images even at higher magnifications.
Generally, the most helpful spotting scope magnification is around 30x or 40x. At these levels, you can easily observe large birds of prey, such as Peregrine Falcons and White-tailed Eagles, at their nest without disturbing them. While a spotting scope is not designed to do this as well as a telescope, it does offer the advantage of being much more portable and lightweight. Most spotting scopes will include a case that can transport the scope. They can also often be mounted to a tripod, making them more stable than a telescope.
Weight
Many birders start with binoculars that can magnify their subject by eight times (8x) or ten times (10x), but the magnification power on a spotting scope takes it to another level. Most spotting scopes offer a range of magnification between 15-20x while zoomed out and 40-60x when fully zoomed in, which turns what might look like a brown blob with some blurry field marks into a detailed image of your favorite bird or other wildlife.
The higher the magnification, the smaller your field of view, so spotting scopes typically have a relatively large objective lens to maintain good image quality at high magnifications. A larger lens also adds to the weight of the spotting scope, so keep that in mind when shopping for one.
The high magnification on a spotting scope makes it prone to image disturbance from even the slightest movement, so these scopes are typically mounted on tripods to stabilize them. If you want to try digiscoping with a spotting scope, be prepared for the expense of a decent tripod.
