Abstract
THE COMET OF 1707.—The elements of this comet's orbit, as calculated by Lacaille and Struyck, bear a certain degree of resemblaace to those of the comet discovered by De Vico at Rome on February 20, 1846 (1846 IV. of our catalogues), to which Van Deinse's definitive calculation assigns a period of revolution of 73 years. The interval between the perihelion passages in 1707 and 1846 would give two periods of 69.1 years; there is consequently a sufficient reason for examining how far the elements of the comet of 1707 represent the observations. It appears to have been discovered by Manfredi at Bologna on November 25, and the place given in the Mémoires of the Paris Academy for that date was in R.A. 308° 25′, Decl. −24° 17′. Pingré in his Cométographie mentions that according to Struyck this position is erroneous, and that ten minutes should be added to the declination and five to the right ascension as printed in the Mémoires, adding that if Lacaille has used the Bologna observation his orbit would be less accurate than that of Struyck. The Bologna observers Manfredi and Stancari found the comet on November 25, in the same field of view of an 8-foot telescope, with two stars, the distance between which they estimated at 9′. At 7h. 14m. 47s. apparent time the centre of the comet was in the right line joining these stars, and its distance from the northernmost star was one-third of the distance between them. It is easy to see from the rough position given, that the stars in question are Piazzi XX., 296 and 298, and carrying back his places, we have for the position of the comet referred to the mean equinox of 1708.0, R.A. 307° 49′.3, Decl. −23° 44′.1. The equation of time was 12m. 37s. sub-tractive from apparent time, and hence the Greenwich mean time of observation was November 25.26163. The place calculated from Lacaille's orbit, first published in his “Leçons d'Astronomie,” differs +7′.2 in R.A. and +5′.6 in Decl., so that it is evident he did not use the position as erroneously deduced in the Mémoires. The agreement of his elements with the Paris observation on December 17 is fairly good; there is a much larger deviation from the approximate places determined at Bologna, on January 13 and 17; but these observations of Manfredi and Stancari are probably affected with very material errors, as such is certainly the case with the deduced position for the night of discovery. So far as can be judged from this partial comparison of Lacaille's elements with observation, the hypothesis of identity of the comet of 1707 with that of 1846 is not supported, but the observations of the former may deserve further discussion.
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Our Astronomical Column . Nature 28, 89–90 (1883). https://doi.org/10.1038/028089a0
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DOI: https://doi.org/10.1038/028089a0