Learn About Spotting Scopes

Why Choose a Spotting Scope?

At magnifications of 7x to 10x, binoculars are sufficient for observing birds that are close up or large birds at moderate distances. For greater magnification, birders turn to spotting scopes, which are telescopes designed specifically for birding. While the design principles of scopes and binoculars share similarities, several unique aspects must be considered when selecting a spotting scope.

Birding scope magnifications range from 10x to 75x. Higher magnification increases the impact of any design defects, requiring the highest quality glass and largest objective lenses for effective use. Without these, high-power scopes can be essentially useless.

Spotting scopes vary in price drastically from a couple hundred dollars to the price of a used car. As with any optical equipment, balance cost against benefits and purchase the best you can afford. Additionally, allocate a portion of your budget for a sturdy tripod to support your scope. For a comprehensive discussion on tripods, see our section on tripods and support systems.

No discussion on birding scopes is complete without mentioning digiscoping, the technique of taking photos with a digital camera through a spotting scope. For regular digiscopers, our digiscoping page offers additional considerations before purchasing a scope.

Construction

Several design factors distinguish scopes from binoculars, beyond the fact that scopes are monocular. To accommodate higher magnification, scopes feature larger objective lenses and longer barrels.

Key Features of Birding Scopes:

• Interchangeable Eyepieces: Most scopes allow for eyepiece changes, specific to the manufacturer and line, enabling users to choose their preferred magnification and field of view.
• Mounting Plate: All birding scopes include a mounting plate for attachment to a tripod or support device.
• Sight Alignment: Many scopes feature a sighting mechanism to help line up birds before viewing through the eyepiece.

Body Design

There are two primary body designs for spotting scopes:

• Straight Scopes: The barrel and eyepiece axes are parallel, making them easier to aim and better for ground or water level viewing.
• Angled Scopes: The eyepiece is angled at 45º to the barrel, which is advantageous for group sharing, viewing birds in tall trees, and using a shorter tripod.

Telescope Designs

Spotting scopes are categorized into three designs: refractor, catadioptric, and reflector.

Refractor

Refracting telescopes use a lens as the objective at one end of a tube, an eyepiece at the other end, and an internal prism to lengthen the optical path and correct the image. Most birding scopes on the market today are refractors.

Catadioptric

Catadioptric telescopes combine lenses and mirrors. In a Schmidt-Cassegrain design, a lens at the front of a short tube directs the image onto a concave mirror at the back. This mirror focuses the image forward onto a small concave mirror near the front, which then focuses the image back through a hole in the main mirror to the eyepiece. While providing greater magnification than refractors of the same weight, they can reverse the image left and right, which may confuse inexperienced users.

Reflector

Reflecting telescopes use a mirror as the objective. Light enters one end of a long tube, strikes a concave mirror at the back, and focuses forward onto a small flat mirror near the front. This mirror diverts the light out the side of the tube to the eyepiece. Currently, there are no widely marketed birding scopes of this design.

Objective Lenses

Objective lenses range in size from 50mm to 100mm. Larger objectives gather more light but are heavier. Image brightness, defined by the exit pupil (objective size divided by magnification), is crucial for high magnification. Generally, exit pupils less than 1.33mm are insufficient for top performance in adverse conditions. To increase light transmission, manufacturers use special glass and coatings, such as "Fluorite," "ED" (extra-low dispersion), "HD" (high density), and "APO" (apochromatic). While higher-priced glass excels in low light or overcast conditions, many users may not notice the difference under normal conditions.

Eyepieces

Most scope manufacturers offer various eyepieces, often sold separately. Some eyepieces fit multiple scope lines, while others are specific to certain models. Common magnifications include 15x, 20x, 22x, 27x, 30x-32x, and 50x. Fixed lenses are still useful despite the rise of high-quality zoom eyepieces. Wide-angle designs (e.g., 30x and 50x) are excellent for activities like sea watching, while long eye relief eyepieces (e.g., 27x) benefit eyeglass wearers and digiscopers.

Angled vs. Straight Scopes

The choice between angled and straight scopes is a matter of personal preference, each having its pros and cons:

• Angled: Easier for group sharing, better for viewing high birds, and allows for a shorter tripod.
• Straight: Easier to aim, less neck strain for level viewing, and less likely to collect rain or dust on the eyepiece.

Focusing Systems

Scopes feature different focusing mechanisms:

• Worm Gear System: Driven by a single knob, offering fast focusing but less precision. Used by brands like Bausch & Lomb, Bushnell, Fuji, Kowa, Pentax, Swift, and Zeiss.
• Helical Gear System: Driven by a ring around the scope body, providing slower coarse focus but better fine control. Used by Nikon and Swarovski.
• Dual Knob System: Combines fast coarse focus with fine control, as seen in Leica scopes.

Conclusions

• Spotting scopes offer closer views than binoculars.
• They vary widely in capability and price.
• Higher magnification requires larger objectives for optimal results.
• Eyepieces are often sold separately, and zoom is not always the best choice.
• Both angled and straight scopes have their unique benefits.
• Focusing systems differ in speed and accuracy.
• Allocate budget for a suitable tripod.

Choosing the right spotting scope involves balancing magnification, glass quality, design preferences, and budget considerations. With careful selection, a spotting scope can significantly enhance your birding experience.