If you’re new to birdwatching, hunting, or astronomy, you might wonder what do the numbers on spotting scopes mean. Those figures, like 20-60×80, are the key to understanding the scope’s power and performance. Let’s break them down so you can choose the right tool for your needs.
Every spotting scope has a model name with two main numbers. The first set, often with an “x” in between, refers to the magnification. The second, larger number is the objective lens diameter in millimeters. These two specs together tell you almost everything about how the scope will behave in the field.
What Do The Numbers On Spotting Scopes Mean
Simply put, the numbers tell you how much bigger an object will appear and how much light the scope can gather. A scope labeled 15-45×60 is a variable power scope. It can magnify from 15 times to 45 times, and it has a front (objective) lens that is 60mm across. A fixed power scope, like a 30×80, only offers one magnification level—30x—with an 80mm objective lens.
Decoding Magnification: The First Number(s)
The magnification number tells you how much closer the subject appears compared to your naked eye. A 20x magnification makes something look 20 times closer. With variable scopes, you get a range.
- Lower Magnification (e.g., 15x-20x): Offers a wider field of view, making it easier to find and follow subjects. The image is also brighter and more stable with less hand shake.
- Higher Magnification (e.g., 45x-60x): Brings distant details into crisp close-up, ideal for identifying fine markings. However, the view narrows, dims, and shows more vibration.
It’s tempting to always use the highest power, but atmosphere conditions like heat haze often make lower powers more effective for a clear view.
Understanding Objective Lens Size: The Second Number
The second number, like 65 or 80, is the diameter of the front lens in millimeters. This is the light-gathering engine of the scope. A larger lens collects more light, which results in a brighter, clearer image, especially in low-light conditions at dawn or dusk.
- Smaller Objective (50-65mm): Lighter, more compact, and easier to carry. Great for daytime use and hiking.
- Larger Objective (80-100mm): Heavier and bulkier, but provides superior image brightness and clarity for detailed, low-light observation.
There is a trade-off between size and performance. You need to match the lens size to when and where you’ll use the scope most.
How Magnification and Lens Size Work Together
These numbers don’t work in isolation. Their relationship creates the scope’s “exit pupil,” which affects image brightness. You can calculate exit pupil by dividing the objective lens size by the magnification.
For example, a 20-60×80 scope at 20x power has an exit pupil of 4mm (80/20=4). At 60x, the exit pupil shrinks to about 1.3mm (80/60≈1.3). A larger exit pupil (over 4mm) gives a very bright image, ideal for low light. As you zoom in, the image naturally gets dimmer.
This is why a 20-60×80 scope often performs better at high power than a 20-60×60 scope—the larger objective lens compensates for the light loss.
Angle of View: The Often-Forgotten Spec
While not in the main model number, the angle of view is crucial. It’s how much horizontal area you can see through the eyepiece, usually in feet at 1000 yards. A wide field of view is fantastic for scanning landscapes or tracking moving animals. Higher magnification always reduces the angle of view.
Choosing the Right Spotting Scope for You
Now that you know what the numbers mean, how do you pick? Your main activities will point you in the right direction.
- For Birdwatching & Wildlife: A versatile zoom like a 15-45×65 or 20-60×80 is excellent. You need lower power for finding birds and higher power for identifying them.
- For Hunting: Durability and low-light performance are key. Look for an 80mm objective lens (e.g., 20-60×80) to see clearly in early morning light. Waterproofing is essential.
- For Astronomy & Long-Range Targets: High power and large lenses win. A fixed 30×80 or a zoom 25-50×80 scope provides the detail needed for celestial viewing or distant target inspection.
- For Hiking & Backpacking: Prioritize weight and size. A compact 15-45×50 or 20-60×60 scope offers a good balance of power and portability without weighing down your pack.
Key Features Beyond the Numbers
The model numbers are just the start. Pay attention to these other critical factors:
- Lens Coatings: Fully multi-coated lenses drastically improve light transmission, contrast, and color fidelity. Never skimp on this.
- Body Design: Angled eyepieces are better for shared use and astronomy. Straight eyepieces are often easier for terrestrial viewing from a blind or window.
- Close Focus: This is the minimum distance at which the scope can focus. A shorter close focus (like 10 feet) is great for butterflies or other nearby subjects.
Common Mistakes to Avoid
When choosing a scope, a few common errors can lead to disapointment. First, don’t assume more magnification is always better. Image quality degrades at the highest zoom on most scopes. Second, pairing a high-magnification eyepiece with a very small objective lens will give you a dark, fuzzy image. Finally, forgetting about the tripod is a big mistake. Any magnification above 30x really requires a steady tripod for a usable view.
Frequently Asked Questions (FAQ)
What does 20-60×80 mean on a spotting scope?
It means the scope offers variable magnification from 20 power to 60 power, and it has an 80mm diameter objective lens for gathering light.
Is a bigger objective lens always better?
Not always. A bigger lens gives a brighter image but makes the scope heavier and larger. For daytime use, a 60-65mm lens is often sufficient and more portable.
What is a good magnification for a spotting scope?
For most purposes, a zoom range starting around 15-20x and going up to 45-60x is very versatile. This lets you scan wide areas and then zoom in for detail.
Can I use a spotting scope without a tripod?
You can at very low magnifications for short periods, but for steady, comfortable viewing—especially at higher powers—a sturdy tripod is absolutely nessecary.
What’s the difference between angled and straight spotting scopes?
Angled scopes (45 or 90 degree) are easier for sharing between people of different heights and for looking at stars. Straight scopes are often more intuitive for following moving targets over level terrain.
How important are lens coatings?
Extremely important. Multi-coated lenses significantly reduce glare and increase brightness and color accuracy. It’s one of the main factors separating budget scopes from quality ones.
Understanding what do the numbers on spotting scopes mean empowers you to make a smart purchase. Remember to balance magnification with lens size based on your primary use. Consider where you’ll use it, how you’ll carry it, and what conditions you’ll face. With the right knowledge, you can select a scope that brings the distant world into perfect view for years of enjoyable observation.