Lens diameter
The diameter of the objective is the front lens of the sight. This parameter is also called "aperture".
This parameter is important primarily for optical sights and their specialized varieties — "night lights" and thermal imagers (see "Type"). The larger the lens, the more light enters it, the higher the image quality and the more efficient the device will work in low light, but the more expensive such optics will cost. It is worth noting here that the requirements for the aperture also depend on the degree of magnification: in other words, especially large lenses are not required for low magnifications. Therefore, relatively small entrance lenses, with a diameter of
25 – 35 mm and even
less, are found in all price categories of classical optics — from low-cost to top. And you can compare by aperture only models with the same maximum magnification, and even then it’s very approximate — it’s worth remembering that image quality also depends heavily on the overall quality of the sight components.
In turn, for night sights, especially those based on image intensifier tubes (see "The principle of operation of night vision devices"), a large aperture is fundamentally important. So a diameter
of 36 to 45 mm is considered very small for such devices and is found only in some digital models, while most nightlights are equipped with lenses of
46 mm or more.
As for collimators, the size of the space that enters the scope depends mainly on the aperture. Moreover, the actual visible size can be changed by setting the sight closer or farther to the eye — the principle of operation of collimators makes this possible. Note also that for models with lenses of a rectangular or similar shape, the size of the lens is usually indicated diagonally.
Field of view at 100 m
The diameter of the area visible through the sight from a distance of 100 m — in other words, the largest distance between two points at which they can be seen simultaneously from this distance. It is also called "linear field of view". This indicator is more convenient for many users than the angular field of view (the angle between the lines connecting the lens and the extreme points of the visible image) — it very clearly describes the capabilities of the device.
In sights with magnification adjustment (see above), both the entire range of width — from maximum to minimum — or only one value of this parameter can be indicated. In the latter case, the largest width of the field of view is usually taken, at the minimum magnification.
Measuring units of the sight
Units of measurement of angles used in the scope - primarily for making corrections using the drums. The same units are often used in marking the goniometric elements of the aiming reticle (see “Measuring units of the reticle”), but there are exceptions, so it would not hurt to clarify this point separately. Nowadays there are two main units:
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MOA. Abbreviation for minute of arc - 1/60th of a degree. Originally, this unit is associated with the English system of measures and is convenient primarily for calculations in yards and inches: at a distance of 100 yards, an angle of 1 MOA corresponds to a linear dimension of approximately 1 ". In the metric system, which is more familiar to us, this gives 2.91 cm at a distance of 100 m. We also note that this unit is a kind of accuracy standard: it is believed that a full-fledged sniper rifle should give a spread of no more than 1 MOA.
—MRAD. The symbol for a milliradian is an angle of one thousandth of a radian (approximately 0.06°). Also in sniper jargon, this unit is called “thousandth”, or “mil”. It is already tied to the metric system: at a distance of 100 m, an angle of 1 MRAD corresponds to a linear dimension of 10 cm (approximately 3.5 times more than 1 MOA).
The choice based on this indicator largely depends on the personal preferences of the shooter. And although “thousands” are generally more convenient for domestic use
...rs, with minimal experience you can successfully use MOA, and also switch between these units and convert one to another without much difficulty. So in general this point is not particularly important.Adjustment division value
The division value of the turrets used in the sight to enter corrections.
The increment value for the correction turret is the angle that the point of impact shifts when rotated by 1 click (“click”). In this case, this angle is indicated in MOA — minutes of arc. For more information about this unit, see "Measuring units of the sight"; and the lower the division value, the more accurately you can set up the sight initially and make corrections in the future. For example, if this indicator is 0.5 MOA — each click will shift the point of impact by about 1.46 cm for every 100 m of distance (that is, 2.91 cm at a distance of 200 m, 4.4 cm at 300 m and so on); and 0.25 MOA will already give only 7.3 mm per click for every 100 m.
The smaller the step and the more accurate the adjustment system, the more expensive it is. Therefore, when choosing, it is worth taking into account the features of the planned application — first of all, the size of the targets and the distance to them; detailed recommendations on this matter are in various manuals on shooting. If we talk about specific values, then the mentioned 0.5 (1/2) MOA are typical mainly for inexpensive and medium scopes, 0.25 (1/4) MOA is a pretty good indicator, and the advanced optics itself allows adjustment in increments of 0.125 (1/8) MOA.
Lens coating
A type of coating used in scope lenses. Anyway, we are talking about the so-called antireflection coating, which is the thinnest film (single or multilayer) on the surface of the lens in contact with air. The properties of this film are chosen in such a way as to minimize the reflection of light from the glass surface. The meaning of this function is not so much to reduce the brightness of glare that can unmask the shooter, but to increase the light transmission of the optics and, accordingly, the quality of the image visible through it.
Modern sights can be equipped with the following types of coatings:
— Illuminating. In this case, the simplest option is implied — an incomplete single-layer coating. The term "incomplete" means that not all lens surfaces are coated (although there may be several coated surfaces). Such enlightenment is inexpensive, however, the image quality is relatively low — in particular, because a single-layer film is most effective only for a part of the visible colour spectrum.
— Full illumination. Fully coated means that all surfaces of the lenses that come into contact with air have a special coating; in this case it is single layer. Such a coating is more expensive than a simple anti-reflective coating, but the quality of the “picture” when using it is higher, because. light distortion at the transitions between glass and air is minimized.
— Multi-layered illuminating. Incomplete AR coating (see above)...using multilayer films. Thanks to multiple layers, the anti-reflective coating covers the entire visible spectrum, which allows you to achieve a brighter image with less colour distortion compared to single-layer coatings; However the price of such devices is higher.
— Full multilayer enlightenment. The most advanced option: multilayer coating on all lens surfaces used in the design of the sight. Features of full and multi-layer coating are described separately above. Here we note that their combination is typical for high-class sights, because. it provides the highest quality image, but it is not cheap.
More features
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Dust-, water protection. Protected housing that prevents dust and moisture from entering the delicate components of the sight. This feature is highly desirable if the sight is planned to be used in adverse conditions — for example, during a long hunting trip, where there is a chance of encountering bad weather. However it is worth considering that the specific degree of protection may be different, it should be clarified according to the documentation for the sight. However, almost all “protected” models are able to endure rain at least without problems.
—
Impact protection. Special protection that prevents damage to the sight during impacts and shocks — for example, by accidental falling or contact with a foreign object. The effectiveness of this protection may vary for different models, but in most cases it at least allows you to transfer the fall onto a hard surface from a height of 1 – 1.5 m. with a high probability it will turn out to be useless — the impact force will be much greater than that for which the device was originally designed. In addition, after any strong impact, the sight will have to be re-aligned. However, additional protection anyway improves the overall strength and reliability of the device.
—
Filling with gas. A feature that is found exclusively in sights with closed cases (see "Design"). Such cases are made airtight, and th
...e internal space in them is filled with an inert gas — for example, nitrogen — with a minimum content of water vapor. Thanks to this, the optical elements of the sight do not fog up from the inside, and metal parts do not oxidize due to contact with moisture. In addition, such an air-tight housing, by definition, is also dust and moisture resistant (see above).
— Rangefinder. A device that allows you to measure distances to objects visible in the scope. Do not confuse this function with rangefinder markings and other similar reticles (see “Reticle type”): in this case we are talking about a separate device, usually in the form of a laser rangefinder. Such equipment greatly simplifies measurements: there is no need to bother with special calculations for the angular dimensions of visible objects, just one click of a button is enough, and the accuracy of laser devices is very high — on the order of several centimeters at distances of hundreds of metres. The main disadvantage of this feature is the high cost; in addition, additional equipment increases the weight and dimensions of the sight. Therefore, built-in rangefinders are found exclusively in professional models designed for high-precision shooting.
— Level. A device that allows you to control the deviation of the sight (and, accordingly, the weapon) from the horizontal position — namely, the tilt to the right / left. Such a need arises primarily with high-precision shooting: even a slight slope, imperceptible to a person, can give a significant deviation, especially at a great distance. Levels may have a different design and principle of operation, but they are always set so that the shooter can see such an indicator at the same time as aiming. For example, in optics (see "Type"), a bubble bulb is placed above the lens or to the side of it, while in "night lights" and thermal imagers, data from an electronic sensor is projected directly into the eyepiece.
— Lantern. A flashlight mounted directly into the body or on the body of the sight. A rather specific function that is rare: at distances where optics are mainly used, a searchlight is needed, for "night lights" an IR illuminator is relevant (see below), collimators are more convenient to use with a separate underbarrel or hand "tactical" flashlight. However, the built-in lamp cannot be called completely useless. So, in optical sights, it is usually combined with a laser designator (see below), allowing you to effectively use the laser in low light conditions. And in the case of a collimator, the LEDs built into the frame are more compact than a separate underbarrel flashlight (which, moreover, can not be installed on every weapon that is compatible with a collimator).
— Laser designator(LTC). Device for quick aiming at short distances. The idea of such a device is extremely simple: a laser beam shows where the weapon is aimed, creating a clearly visible mark at the point of impact. This allows you to shoot accurately, even without looking into the main sight — including "from the hip" and from other emergency positions, which is especially useful in situations requiring maximum reaction speed. LCC is relevant only at minimum distances, but this is not a drawback, but a feature that can turn out to be a definite advantage. For example, a "laser" can be a great addition to a telescopic sight, which by itself is useless at short distances.
— Compatibility with night vision devices. Possibility of using the sight with separate night vision devices. Most often, this feature is found in collimator sights (see "Type") — it means that the brightness and colour of the collimator mark make it possible to clearly see it even through night vision devices. But optical models with such compatibility are extremely rare: firstly, it is technically difficult to implement, and secondly, for sniper shooting in the dark, there are specialized night and thermal imaging sights that are more convenient and effective than a combination of night vision devices with classic optics.Power source
The type of power used in the scope, in fact, describes the type of autonomous element (accumulator or battery) that the device is designed for.
The most popular elements in modern sights are CR2032 elements — characteristic "pills" with a diameter of 20 mm and a thickness of about 3 mm. Their shape fits very well into the layout of both optics and classical collimators (see "Type"), and the capacity, although relatively low, is quite sufficient for normal operation for a long time, because the power consumption of these types of sights is low. But in more “gluttonous” night, thermal imaging (see ibid) and holographic (see above) models, more solid batteries are usually used — most often either a pair of standard “finger” AA cells, or a 3.7 V CR123 element (diameter 17.5 mm, length 35 mm). In this case, the sight can be compatible with either one of these types, or both. It is also worth noting that AA and CR123 elements are also available as rechargeable batteries, which can be perfect for frequent use of the scope.
Weapon compatibility
The weapon class that this scope can be used with.
Different classes of weapons differ in the energy of the shot and, accordingly, the recoil force that the sight must endure without consequences. It is the maximum allowable energy of the shot (muzzle energy) that in this case is the main criterion for classifying the sight into one of the categories:
light pneumatics,
rifles and shotguns,
large caliber. It is worth saying that such a division is somewhat arbitrary — see details in separate paragraphs; here is their detailed description:
— Lightweight pneumatics. Sights designed for weapons that practically do not give recoil — such as air PCP rifles, spring-piston “breaks” with muzzle energy up to 7.5 J, carbines chambered for Flaubert, as well as airsoft drives. Such models are definitely not suitable for firearms: they do not tolerate even the recoil from small-caliber rifles, not to mention more serious use. And even pneumatics have their limitations — in particular, powerful (more than 7.5 J) spring-piston models give significant returns with strong vibrations, and in pistols with the Blow-back system, noticeable concussions occur not because of the shot itself, but from -for the work of automation. So it is better to equip these types of weapons with more durable and reliable sights.
— Rifles and shotguns. Sights that can be used with
...rifles of small and medium calibers, as well as smoothbore weapons (shotguns). They have a solid construction that allows them to endure rather strong recoil and accompanying vibrations without consequences, but the specific restriction on the allowable muzzle energy (and, accordingly, the calibers and ammunition used) may be different. However, scopes in this category are usually able to safely carry at least 2500 J — this is enough for rifled calibers 5.45x39, 7.62x39 and .223, as well as for 12-gauge rifle cartridges with a standard weight of gunpowder. And in many models, the maximum allowable energy can reach 3500 J and even 4000 J (the smallest values \u200b\u200bnecessary for full-fledged use with .308 and 7.62x54R calibers, respectively). At the same time, for reinforced magnum ammunition, as well as for some powerful (though not large) calibers, such a sight may still not be enough.
— Large-caliber. The most durable and reliable sights, designed for muzzle energy of 4000 J and above. Because of this, they can be used even with large-caliber firearms, as well as with some powerful calibers that are not formally large — for example, .300 Win and .338 Lapua Magnum. The specific restriction on muzzle energy, again, may be different, but if you are looking for a sight for a caliber more powerful than 7.62x54R or for reinforced rifle ammunition like 12x76, you should definitely pay attention to this category.
Separately, it is worth noting that “firearm” sights, even quite durable and reliable, are not recommended to be installed on pneumatics with a spring-piston mechanism or a gas spring. The fact is that such rifles have a specific recoil, directed forward rather than backward, moreover, giving sharp vibrations in different directions; and although the force of such recoil is low, it can still adversely affect the sight, which was not originally designed for it.Fastening type included
The type
of mount supplied with the scope.
For normal mounting on a weapon, this mount must match the type of seat for the scope. The most popular types of mounts nowadays are
on the Weaver / Picatinny rail and on
the dovetail ; branded latches are noticeably less common, and some sights
are supplied without mounts at all — this allows you to choose the option at your discretion. Here is a detailed description of specific options:
— On the Weaver / Picatinny rail. Fastening on a standard bar (“rail”) Weaver or Picatinny rail. It is considered the Western standard for installing a weapon body kit, but nowadays it is widely used around the world. It is worth noting that these types of slats, although similar in design, are not the same. They both have a T-shaped profile and transverse slots that allow you to securely fix the installed accessory in the chosen place, but differ in the size and location of these slots: they are wider in Picatinny rails and have a standard distance between centers. In fact, this leads to the fact that accessories for Weaver rails can easily fit on Picatinny rails, but not vice versa. In addition, Picatinny is considered more of a military standard, and civilian weapons are equipped mainly with Weaver rails. Thus, most of the complete rail mounts found among modern sights are designed specifi
...cally for the Weaver rail, as it is more common and universal. However, exceptions are possible, so this nuance needs to be specified separately.
— "Dovetail". The seat of this type has a cross-sectional view of an inverted trapezoid, and the mount provides protrusions on both sides, which, when the sight is installed, “cover” this trapezoid. This type of mount is found mainly in air and sporting rifles, as well as in hunting weapons of a classic design. In the latter case, this choice is also due to aesthetic considerations — these mounts look neater than the gear "rails" of Weaver and Picatinny rails.
— Firm. Various specific fastenings not related to the standards described above. Often they are made not just for the products of a particular brand, but also for strictly defined models of weapons; one of the characteristic examples is the original seat on the high-end "sniper" Blaser R93. Branded devices can have a rather original design — for example, in some collimators for shotguns, a plate is used that is fixed between the butt and the receiver. In general, due to limitations in application, such fasteners are usually provided not as the only option, but as one of the options, in addition to the bar and/or dovetail.
Separately, it is worth touching on situations where several types of mounts are indicated in the characteristics of the sight at once. Most often this means that this model is available in different configurations, but there are other, more specific options — the presence of several types of mounts in the kit at once, an adapter from one type to another, or even a universal retainer that is also compatible with Weaver / Picatinny rails, and with a dovetail. Such details in each case should be clarified separately.