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A 1951 USAF resolution test chart is a microscopic optical resolution test device originally defined by the U.S. Air Force MIL-STD-150A standard of 1951. The design provides numerous small target shapes exhibiting a stepped assortment of precise spatial frequency specimens.
Nightforce Optics, Inc. is an American manufacturer of high-end telescopic sights, spotting scopes and mounting accessories, based in Lavonia, Georgia with factory headquarters in Orofino, Idaho. Established in 1992, the company is the optic subsidiary of Lightforce Performance Lighting , an Australian manufacturer of specialty lighting ...
An alternative variant uses perpendicular hash lines instead of dots, and is known as the mil-hash reticle. Such graduated reticles, along with those with MOA-based increments, are collectively and unofficially called "milling reticles", and have gained significant acceptance in NATO and other military and law enforcement organizations.
If a rifle scope has mrad markings in the reticle (or there is a spotting scope with an mrad reticle available), the reticle can be used to measure how many mrads to correct a shot even without knowing the shooting distance. For instance, assuming a precise shot fired by an experienced shooter missed the target by 0.8 mrad as seen through an ...
Stadiametric rangefinding, or the stadia method, is a technique of measuring distances with a telescopic instrument.The term stadia comes from a Greek unit of length Stadion (equal to 600 Greek feet, pous) which was the typical length of a sports stadium of the time.
Reticle burn-in was also addressed. One issue that persists even in production models is the tendency for the projected reticle pattern to become washed out in bright light. This can be somewhat mitigated by adjusting the Reticle Brightness knob to its brightest position and keeping the Tube Brightness knob as low as possible.
The 10 reticle hashmarks in the horizontal plane can be used to compensate for wind or moving targets and can also be used for additional stadiametric rangefinding purposes, since they are spaced at 1 milliradian intervals, meaning if an object is 5 m wide it will appear 10 hashmarks wide at 500 m.
A Snellen chart is an eye chart that can be used to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart in 1862 as a measurement tool for the acuity formula developed by his professor Franciscus Cornelius Donders .