theecliptic. The rate of retro-gradation is 19° 19 in a year,making a whole circle in about18.6 years. (178.) We are now pre-pared to be a little more defi-nite, and inquire as to theamount of some of the lunarirregularities. Let S be the mass of thesun, E that of the earth, andm the moon, situated… … represented in the figure at D.) S The attraction of the sun on the earth is —-, the attrac-ts2 LUNAR PERTURBATIONS 189 tion of the sun on the moon is — ; and the attraction of the -— earth and moon, on the moon, is * . ( Art. 156.) Let the line D B, the diagonal of the parallelogram A C, bethe…
Astronomy
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![An illustration from Nicolai Copernici Torinensis De reuolutionibus orbium coelestium, libri VI : Habes in hoc opere iam recens nato, & aedito, studiose lector, motus stellarum, tam fixarum, quàm erraticarum, cum ex ueteribus, tum etiam ex recentibus obseruationibus restitutos: & nouis insuper ac admirabilibus hypothesibus ornatos. Habes etiam tabulas expeditissimas, ex quibus eosdem ad quoduis tempus quàm facillime caculare poteris. Igitur eme, lege, fruere. [Line in Greek] (1543)](https://img.insideoutlibrary.com/img/200/ia-nicolaicopernici00cope-388-268.webp)
