フリードリヒ・ヴィルヘルム・ベッセル
To support a line standard, one wishes to minimise the "linear", rather than angular, motion of the ends. The Bessel points (after Friedrich Bessel) are the points at which the length of the beam is maximized. Because this is a maximum, the effect of a small positioning error is proportional to the square of the error, an even smaller amount.