If you’re new to birdwatching, hunting, or astronomy, you might look at a spotting scope and wonder what the numbers mean on spotting scopes. These figures, like 20-60×80 or 15-45×65, are the key to understanding the scope’s power and capability. They tell you everything about how much you can magnify an image and how bright and clear it will appear. Let’s break down this code so you can choose the right tool for your adventures.
Every spotting scope has a model name that includes a set of numbers separated by an ‘x’. It might look confusing at first, but it’s actually a simple formula. The numbers before the ‘x’ refer to magnification, and the number after refers to the objective lens diameter. Once you know this, you can quickly compare different models and understand their strengths and weaknesses.
What Do The Numbers Mean On Spotting Scopes
This is the core question. The numbers represent the scope’s vital specifications: its magnification range and the size of its front (objective) lens. They are always presented in a standard format. For example, a scope labeled 20-60×80 has a variable magnification from 20x to 60x and an objective lens that is 80 millimeters in diameter. This simple code is your guide to performance.
Decoding the Magnification Number (The First Part)
The first number, or pair of numbers, indicates magnification. If you see a single number like 30x, it’s a fixed-power scope. Most modern scopes, however, are zoom scopes, shown as a range like 20-60x.
- What Magnification Does: It tells you how many times closer the target will appear compared to your naked eye. At 20x, an object looks 20 times closer. At 60x, it looks 60 times closer.
- Lower Magnification (e.g., 20x): Offers a wider field of view, making it easier to locate objects. The image is generally brighter and more stable, with less shake from hand movement. It’s ideal for scanning landscapes or watching larger wildlife.
- Higher Magnification (e.g., 60x): Brings distant details into sharp focus, like reading leg bands on birds or examining antler points. However, the field of view narrows, image brightness can dim, and any shake is greatly amplified, necessitating a sturdy tripod.
Understanding the Objective Lens Size (The Second Part)
The number after the ‘x’ is the diameter of the objective lens in millimeters. This is the large lens at the front of the scope that gathers light.
- What Lens Size Does: A larger lens captures more light. More light means a brighter, clearer image, especially in low-light conditions like dawn, dusk, or under a thick forest canopy.
- Common Sizes: Typical sizes range from 50mm to 100mm. A 65mm lens is a great all-around choice. An 80mm or larger lens is excellent for low-light but results in a heavier, bulkier scope.
- The Trade-off: Bigger lenses mean better light gathering, but they also mean more weight and size to carry. You must balance your need for image quality with your willingness to carry the equipment.
How Magnification and Lens Size Work Together
These two numbers have a direct relationship. Think of the objective lens as a bucket collecting light (rain). The magnification is like spreading that collected water over a surface.
- At low magnification, you’re spreading the light over a small area (a small puddle), so the image is bright.
- At high magnification, you’re stretching the same amount of light over a much larger area (a thin film), which can make the image darker and less distinct.
This is why a scope with a larger objective lens (a bigger bucket) performs better at high zoom levels—it simply has more light to begin with. A 20-60×80 scope will generally provide a brighter image at 60x than a 20-60×60 scope would.
What is Exit Pupil and Why It Matters
This relationship is measured by a useful concept called exit pupil. You can calculate it easily: just divide the objective lens diameter by the magnification.
Exit Pupil = Objective Lens Diameter / Magnification
For a 20-60×80 scope:
- At 20x: Exit Pupil = 80/20 = 4mm (a bright, wide beam for your eye)
- At 60x: Exit Pupil = 80/60 ≈ 1.33mm (a narrower, dimmer beam)
A larger exit pupil (above 2-3mm) gives a brighter image that’s easier to look through, especialy as your eye moves. An exit pupil smaller than your eye’s pupil in low light (about 7mm) will seem dim.
Other Important Numbers and Codes
Beyond the main numbers, you might see other specifications.
- Field of View (FOV): Often listed in feet at 1000 yards or meters at 1000m. A wider FOV means you see more area at once, which is great for tracking moving subjects.
- Close Focus: The minimum distance at which the scope can focus. Important for butterfly watching or studying details on close objects.
- Eye Relief: The distance your eye can be from the eyepiece and still see the full image. Crucial for eyeglass wearers; look for 15mm or more.
- Lens Coatings: Terms like “Fully Multi-coated” mean lenses have multiple anti-reflective layers, which maximize light transmission and image contrast.
Choosing the Right Numbers for Your Needs
Now, let’s apply this knowledge. Here’s a simple guide based on common activities.
- Birdwatching & General Wildlife: A versatile zoom like 15-45x or 20-60x paired with a 65mm or 80mm objective is perfect. The zoom range offers flexibility, and the lens size ensures good light.
- Hunting: For backpacking, a compact 15-45×65 or similar is excellent. For stationary glassing from a stand, a larger 20-60×80 or even an 85mm model provides superior detail in early morning light.
- Astronomy & Long-Range Observation: Prioritize large aperture (80mm+) for maximum light gathering. A zoom range starting at a lower power (like 15-45x) helps locate celestial objects before zooming in.
- Travel & Hiking: Weight is key. Look for smaller objective lenses (50-65mm) with a reasonable zoom. A 16-48×60 scope offers a great balance of power and portability.
FAQ: Your Questions Answered
Q: Is a higher magnification always better?
A: No. Higher magnification amplifies image shake, reduces brightness, and narrows your field of view. It’s best used on a rock-solid tripod for examining stationary details.
Q: What does a bigger objective lens do?
A: It gathers more light, resulting in a brighter and often sharper image, which is critical in low-light conditions. The downside is increased size and weight.
Q: What spotting scope numbers are best for birding?
A: Most birders prefer a scope like a 20-60×80. The zoom allows for both locating birds (at 20x) and identifying fine details (at 60x), while the 80mm lens gives good clarity.
Q: Can I use a spotting scope without a tripod?
A: At lower magnifications (below 30x), you might manage briefly. For any serious use, especially at higher powers, a tripod is absolutely essential for a steady view. Hand-holding at 60x is nearly impossible.
Q: What’s the difference between 60mm and 80mm?
A: The 80mm lens is about 78% larger in area, meaning it collects significantly more light. This makes the 80mm model superior at dawn, dusk, or under cloudy skies, though it is larger and heavier.
Understanding what the numbers mean on spotting scopes empowers you to make a smart purchase. Remember to consider where and how you’ll use it most. A scope that’s perfect for a stationary hunter may be to heavy for a long-distance hiker. By balancing magnification, lens size, and the resulting factors like brightness and weight, you’ll find the ideal scope to bring the distant world beautifully into view.