密位
A milliradian (SI-symbol mrad, sometimes also abbreviated mil) is an SI [国际单位制] derived unit for angular measurement which is defined as a thousandth of a radian (0.001 radian).
Use of the milliradian is practical because it is concerned with small angles, and when using radians the small angle approximation shows that the angle approximates to the sine of the angle, that is sin(θ) ≈ θ. This allows a user to dispense with trigonometry and use simple ratios to determine size and distance with high accuracy for rifle and short distance artillery calculations by using the handy property of subtension:
- One mrad approximately subtends one meter at a distance of one thousand meters.
- 弧长 = 半径 × 圆心角
- 1弧度所对的弧的长度=半径; 1弧度=360º/2π≈57º；等边三角形的顶角是60º
For small observed angles (green) the arc length (blue) approaches the subtension (orange).
subtend - (of a chord or the side of a triangle) be opposite to (an arc or angle) 角的对边。
Milliradians are used in adjustment of firearm sights by adjusting the angle of the sight compared to the barrel [枪管] (up, down, left, or right). Milliradians are also used for comparing shot groupings, or to compare the difficulty of hitting different sized shooting targets at different distances. A shot grouping, or simply group, is the collective pattern of projectile impacts on a target from multiple consecutive shots taken in one shooting session.
When using a scope with both mrad adjustment and a reticle [标线; 分划线; 十字线] with mrad markings (called an “mrad/mrad scope”), the shooter can use the reticle as a ‘ruler’ to count the number of mrads a shot was off-target, which directly translates to the sight adjustment needed to hit the target with a follow up shot. Optics [镜片] with mrad markings in the reticle can also be used to make a range estimation of a known size target, or vice versa, to determine a target size if the distance is known, a practice called “milling”.
PSO-1 reticle, the bottom-left corner can be used to determine the distance from a 170 cm tall target (expected average height of an enemy combatant).
Reticle is a network of fine lines, dots, cross hairs, or wires in the focal plane of the eyepiece of an optical instrument.
cross hair - 十字瞄准线
The Soviet PSO-1 (Pritsel Snaipersky Optichesky, "Optical Sniper Sight") telescopic sight was at the time of its introduction (around 1964), the most technically advanced telescopic sight ever designed for a mass-production designated marksman or sniper rifle. The PSO-1 telescopic sight is manufactured in Russia by the Novosibirsk instrument-making factory (NPZ Optics State Plant) and is issued with the Russian military Dragunov sniper rifle. 苏联PSO-1（Pritsel Snaipersky Optichesky，“光学狙击瞄准具”）望远镜瞄准具在推出时（大约1964年），是有史以来为大规模生产指定射手或狙击步枪设计的技术最先进的望远镜瞄准具。PSO-1望远镜瞄准具由新西伯利亚仪器制造厂（NPZ光学国家工厂）在俄罗斯制造，并配有俄罗斯军用德拉古诺夫狙击步枪。
Optical specifications and dimensions
- Magnification: 4x
- Objective diameter: 24 mm
- Field of view: 6°
- Exit pupil: 6 mm
- Eye relief: 80 mm
- Limiting optical resolution: 12 SOA
- Power supply for reticle illumination: 1 AA battery
- Weight: 0.6 kg
- Overall dimensions: (L x W x H): 375 x 70 x 132 mm
Parallax is when an object appears to change its position because the person or instrument observing it has changed their position. Windage is the air resistance of a moving object. Ocular means relating to the eyes or the ability to see.
What Is A Rifle Scope Objective Diameter
六级/考研单词: abbreviation, derive, sinister, dispense, rifle, artillery, meter, arc, chord, triangle, shot, collective, multiple, consecutive, translate, optic, vice, mill, telescope, designate, manufacture, issue, militant, dimension, magnify, diameter, resolve, illuminate
