n-fold right-handed screw axis
1Clockwise — For other meanings of clockwise, see Clockwise (disambiguation). The clockwise direction Circular motion can occur in two possible directions. A clockwise (typically abbreviated as CW) motion is one that proceeds in the same direction as a clock… …
2History of the single-lens reflex camera — The history of the single lens reflex camera predates the invention of photography in 1826/27 by one and a half centuries with the use of a reflex mirror in a camera obscura first described in 1676. Such SLR devices were popular as drawing aids… …
