Abstract
THE ellipticity of the Earth causes perturbations of the elements of the Moon's orbit with a period of 18.6 years. The value of the ellipticity used in Brown's “Tables of the Motion of the Moon” and in the “Improved Lunar Ephemeris” is 1/294. As has been pointed out elsewhere1, the correction to be applied to the tabular longitude of the Moon in order to reduce it to ellipticity 1/297 is equal to −0.149″ sin Ω, where Ω is the longitude of the Moon's node. This is equivalent to a correction of + 0.271 s. sin Ω to ΔT as defined by the International Astronomical Union2. Recent observations of artificial Earth satellites indicate that the true value of the ellipticity may be nearer 1/298 (ref. 3), in which case the correction to be applied to ΔT is + 0.36 s. sin Ω.
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References
Murray, C. A., Mon. Not. Roy. Astron. Soc., 116, 477 (1956).
Trans. Int. Astron. Union, 8, 66 (1954).
Cook, A. H., Geophys. J., 1, 341 (1958).
Markowitz, W., Hall, R. Glenn, Essen, L., and Perry, J. V. L., Phys. Rev. Letters, 1, 105 (1958).
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MURRAY, C. An Error in the Determination of ΔT from the Lunar Ephemeris and the Frequency of Caesium in Terms of U.T. + ΔT . Nature 184, 441–442 (1959). https://doi.org/10.1038/184441b0
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DOI: https://doi.org/10.1038/184441b0
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