How to Choose Spotting Scopes

Next to binoculars and field guides, birders rely on scopes more than any other tool due to their higher magnification, which allows for detailed observation of distant birds that binoculars cannot achieve. Scopes are designed to be mounted on tripods for stability under normal conditions.

Scope Design and Terminology

Scope design and terminology are detailed in our All About Optics - Scopes section. If you are new to this topic, we recommend reading it before proceeding.

Design Types There are three basic scope designs: refractive, Newtonian, and catadioptric. Most birding scopes are refractive, with a few catadioptric models available. Newtonian scopes are rare and hard to find. Catadioptric scopes, though they offer superior image quality at higher magnifications, are significantly more expensive and less durable for birding use. For this reason, we focus on refractive scopes.

Body Designs Refractor scopes come in two body designs: angled and straight. Each design has its proponents and specific advantages:

Angled Scopes:

• Easier to share with a group.
• Higher eyepoint allows the use of a shorter tripod.
• Better for observing birds in trees or soaring overhead.

Straight Scopes:

• Less strain on the neck for level viewing.
• Reduced risk of collecting rain or dust on the eyepiece.
• Easier for viewing birds on the ground, water, or below a cliff.
• Easier to aim for inexperienced users.

Consider your typical birding activities to decide between angled and straight scopes.

Magnification Scopes offer magnification ranging from 15x to 75x. While higher magnification allows for greater detail, it also reduces the exit pupil size, making it harder to maintain image quality in lower light conditions. Exceeding 1.33mm in exit pupil size can result in reduced image quality and increased distortion from heat waves and scope movement.

Objective Lenses Size: Objective lens diameters vary, with common sizes including 50mm, 60-65mm, 77-85mm, and above 85mm. Larger lenses gather more light, enhancing image brightness and detail in low-light conditions. Choose the largest objective lens you are willing to carry to maximize image quality.

Glass Quality: High-quality scopes use special glass, such as Extra-low Dispersion (ED), Fluorite (FL), or High Density (HD) glass, to correct optical aberrations. These materials focus all wavelengths of light at the same point (apochromatic) or near the same point (achromatic), resulting in sharper images, better detail, and reduced eye strain. While ED/FL/HD scopes are more expensive, they offer significant improvements in view quality.

Eyepieces The eyepiece determines magnification, with shorter focal length eyepieces providing greater magnification. Advances in zoom lens technology have made zoom eyepieces popular among birders, allowing for low-power scanning and high-power detail observation. Fixed wide-angle eyepieces (30x to 50x) are favored by sea and hawk watchers, while long eye relief eyepieces benefit eyeglass wearers and digiscopers. Some manufacturers use the same eyepiece mount for different scope sizes, offering variable magnifications.

Focusing Mechanisms Refractor scopes use three focusing mechanisms: single knob, double knob, and helical. Single knob is precise but slow, double knob (available on Leica) offers both quick and fine focusing, and helical focus (found on Swarovski and some Nikon scopes) allows rapid focus changes. Expect future scopes to feature variable speed focus similar to Brunton binoculars.

Photography Using Scopes

Scopes can be used for photography in two ways:

• Camera Adapter: Attach a 35mm SLR to the scope for fixed focal length photography using the camera's viewfinder.
• Digiscoping: Use a digital camera placed at the eyepiece of the scope. Detailed guidance on this method is available in our Digiscoping section.