Our Astronomical Column

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    THE SATURNIAN SATELLITE, HYPERION. — Prof. Asaph Hall, in Astron. Nach., No. 2,137, publishes an ephemeris of this faint object about the approaching opposition of Saturn, with the view to facilitate observations, especially near the conjunctions. He remarks that although the satellite was discovered (by Bond and Lassell) nearly thirty years since, the difficulty of observing it has been so great that no satisfactory determination of its orbit has been practicable; most of the observations being made near the elongations, the position of the plane of the orbit is not accurately deducible therefrom, though it probably does not coincide with the plane of the ring, but appears to lie between those of Titan and Japetus. With the view to assist observation in the present year Prof. A. Hall has calculated elements from his observations in 1875, which may be stated as follows:—Perisaturnium passage. 1875, August 24.0036 mean time at Washington; distance of perisaturnium from the node 40° 0′, eccentricity 0.125, semi-axis major 214″.22, period of revolution 21.3113 mean solar days. For the reason stated above it is supposed for this approximate orbit that its plane coincides with that of the ring, the node of which on the earth's equator is assumed to be in 126° 9′.1, and its inclination thereto 7° 3′.8. From these data auxiliary quantities and an ephemeris for Washington midnight, August 1-September 15, are added, and it is suggested that with the aid of the former comprising the interval June 1-December 28 a more accurate calculation may be made by Mr. Marth's formulae.

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    Our Astronomical Column . Nature 16, 169 (1877) doi:10.1038/016169a0

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