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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.
The RCT has a wider field of view free of optical errors compared to a more traditional reflecting telescope configuration. Since the mid 20th century, a majority of large professional research telescopes have been Ritchey–Chrétien configurations; some well-known examples are the Hubble Space Telescope , the Keck telescopes and the ESO Very ...
The most common location for a frame-mounted bottle cage is on the top side of the downtube. The most common location for a second frame-mounted bottle cage is on the front side of the seat tube. Small bikes and mountain bikes with rear suspension often do not have enough room for two bottle cages inside the main frame triangle. Some mountain ...
Rack with sample component sizes including an A/V half-rack unit. A rack unit (abbreviated U or RU) is a unit of measure defined as 1 + 3 ⁄ 4 inches (44.45 mm). [1] [2] It is most frequently used as a measurement of the overall height of 19-inch and 23-inch rack frames, as well as the height of equipment that mounts in these frames, whereby the height of the frame or equipment is expressed ...
The only significant difference between the MIL-STD-1913 rail and the similar Weaver rail mount are the size and shapes of the slots. Whereas the earlier Weaver rail is modified from a low, wide dovetail rail and has rounded slots, the 1913 rail has a more pronounced angular section and square-bottomed slots. This means that an accessory ...
The Picatinny rail has a similar profile to the Weaver, but the recoil groove width of the Picatinny rail is 0.206 in (5.23 mm) versus 0.180 in (4.57 mm) of the Weaver rail/mount, and by contrast with the Weaver, the spacing of the Picatinny recoil groove centers is consistent, at 0.394 in (10.01 mm). [5]
A rail system mounted on top of a SIG SG 550 A dovetail rail on a rifle receiver for mounting a sight. A rail integration system (RIS; also called a rail accessory system (RAS), rail interface system, rail system, mount, base, gun rail, or simply a rail [1]) is a generic term for any standardized attachment system for mounting firearm accessories via bar-like straight brackets (i.e. "rails ...
Locomotive frame of a LNER Gresley Pacific locomotive during construction. A locomotive frame is the structure that forms the backbone of the railway locomotive, giving it strength and supporting the superstructure elements such as a cab, boiler or bodywork. The vast majority of locomotives have had a frame structure of some kind.