The Reticle Cursor-Obscure, Brilliant, and Doomed

摘要

The usual 10-inch linear slide rule requires estimation of the fourth digit at the left end of the C/D scales and estimation of the third digit at the right end of these scales. This limited precision [1] has been a challenge to innovators for decades. The quest for more signifiicant digits has produced slide rules with longer scales, magnifying cursors, and refined measuring devices such as the Goulding cursor. [2] However, until recently, we were unaware of any application of the reticle principle to the more precise reading of the slide rule scales.