The distance of the lucid points was the tangent of the magnified angles subtended by the stars to a radius of io ft.
Tangent sights were not much trusted at first.
The tangent sight was graduated in yards as well as degrees and had also a fuze scale.
With the exception of the addition of a pin-hole to the tangent sight and cross wires to the fore-sight, and of minor improvements, and Field of the introduction of French's crossbar sight and the artillery reciprocating sight, of which later, no great advance was sights.
In practice, tangent sights were graduated graphically from large scale drawings.