1. Telescope Notation Methods
The basic way to denote a telescope is: magnification x objective lens diameter (in mm). There are only slight differences in how different types of telescopes are specified, but they all follow this pattern. Here's a breakdown:
For fixed-magnification telescopes (the most common type), the notation is: magnification x objective lens diameter (in mm). For example, 7x35 means the telescope has 7x magnification and a 35mm objective lens; 10x50 means 10x magnification and a 50mm objective lens.
For zoom telescopes, the notation is: "minimum magnification-maximum magnification x objective lens diameter (in mm)." For example, 8-25x25 means the telescope has a magnification range from 8x to 25x, with a 25mm objective lens.
For fixed-zoom telescopes, the notation is: low magnification/high magnification (/even higher magnification) x objective lens diameter (in mm). Sometimes it’s also expressed as minimum magnification-maximum magnification x objective lens diameter (in mm). For instance, 15/30*80 refers to a telescope with fixed magnifications of 15x and 30x and an 80mm objective lens.
For waterproof telescopes, the notation usually includes WP (Waterproof) after the model number. For example, 8X30WP indicates an 8x magnification, 30mm objective lens waterproof telescope.
For wide-angle telescopes, the notation typically includes WA (Wide Angle) after the model number. For example, 7X35WA refers to a 7x magnification, 35mm objective lens wide-angle telescope.
Some dealers misleadingly multiply the two numbers and claim that product as the telescope’s magnification to deceive consumers, which is unethical. Even worse, some arbitrarily inflate both numbers to trick buyers. I once saw a DCF telescope labeled 10x25, yet its specifications claimed it was 990x99990—goodness gracious, what does a 990x magnification telescope with a 99990mm objective lens even mean?
2. What Does Telescope Magnification Mean?
A telescope’s magnification refers to its ability to bring objects closer. For example, using a 7x telescope to observe an object gives you a view similar to seeing an object 100 meters away with the naked eye—but from 700 meters away (though environmental factors may slightly degrade the image quality). Many people assume that the higher the magnification, the better. Some dealers and manufacturers exploit this by advertising falsely high magnifications to attract and mislead consumers—some telescopes on the market are even labeled as 990x magnification. In reality, a telescope’s appropriate magnification depends on its objective lens diameter and how it is used: larger-diameter lenses can handle higher magnifications, and mounted telescopes can have higher magnifications than handheld ones. The higher the magnification, the lower the stability, the narrower and darker the field of view, and the greater the impact of shaking, breathing movements, and air turbulence. For handheld use, a magnification between 7x and 10x is ideal—preferably not exceeding 12x. Once the magnification goes beyond 12x, handheld observation becomes very inconvenient. Military telescopes around the world mostly range between 7x and 10x, such as China’s military scopes, which are mainly 7x and 8x, because clear and stable imaging is crucial.
3. What Does Telescope Aperture Mean?
Aperture refers to the diameter of the telescope’s objective lens. The larger the aperture, the greater the field of view and brightness, which is beneficial for observing in dim light. However, a larger aperture also means a larger physical size. Typically, you can choose from apertures between 21mm and 50mm based on your needs. In recent years, some large-aperture telescopes with diameters of 70mm, 80mm, or even 100mm have appeared on the market—they are quite bulky and often come with mounts.
4. What Is a Telescope’s Field of View?
Field of View (FOV) refers to the extent of the observable area at a given distance. The wider the FOV, the broader and more comfortable the viewing experience. FOV is generally expressed in two ways: either as the visible width (in meters or feet) at a certain distance (like 1000 meters or 1000 yards), or as an angular measurement (in degrees). The three common formats are: 1. Direct angle, e.g., angle of view: 9°; 2. Visible width at a certain distance, e.g., Field of view: 158m/1000m; 3. Visible width in feet at 1000 yards, which is essentially the same as the second format, e.g., Field of view: 288ft/1000y. Generally speaking, the larger the aperture and the lower the magnification, the wider the field of view—but the eyepiece design also plays a key role.