The Moon's Librations

Koziel's results on the librations are rediscussed. Serious departures from independence of the errors are found and allowed for. The results are β = 0.000 6271 ± 0.000 0010 γ = 0.000 2362 ± 0.000 0082. These do not differ much from Koziel's values but the uncertainties are larger. Both are consistent with results previously derived by comparison of those of different authors, and γ is consistent with a reinterpretation of a result of Yakovkin. γ is greater than the critical value ( f less than its); this agrees with Koziel. The effect of elasticity is considered. It is shown that the elastic strain contributes nothing to the librations but would affect the perturbations of a satellite. Allowance for it reduces Michael's estimate of 0.4015 for $$C/{Ma}^{2}\,\text{to}\,0.4001\,\pm\,0.0030$$ , which would be consistent with either uniform density or with one found in 1936, which took account of probable variations of density.