L = f(S) function computed here for the geometry of the eclipse: S is the surface of the solar crescent above the Earth’s reference limb – as observed from the Moon at the location of either fiber A or B within the penumbra. From there, the diameters of the Earth and the Sun are 6768.0 and 1890.6 arcsec respectively. This geometry implies the relation shown between the length of the Earth’s limb covered by the Sun L, and the surface of the solar crescent, normalized to the total solar disk surface S_⊙ as seen from the Moon. Since S_A / S_⊙ or S_B / S_⊙ are known from observations, the corresponding arcs lengths L_A or L_B are also known, and thus h(λ) evaluated.