Mr. Bond also presented the subjoined OBSERVATIONS ON MAUVAIS'S COMET OF JULY 4TH, 1847. Cambridge Mean Solar Time. 1847. d. h. m. 8. July 14 11 45 20 10 26 23 10 46 Comet's A. R. 1 Dec. N. h. m. 8. 16 20 Star of Comparison. A. R. 85 14 h. m. S, No. of Dec. N. Comp. 4 4 13 59 26.7 80 53 00 13 50 33.73 80 40 412 54 13 34 00.8 78 14 03 13 42 04.80 78 49 50.0 24 10 06 30 13 28 35.1 77 22 27 13 32 41.03 77 19 41.6 5 27 10 49 10 13 15 55.5 74 41 23 13 00 05.37 73 50 40 5.6 31 10 13 12 13 05 59.4 71 14 11 12 53 43 30 71 25 22.0 Aug. 3 10 32 48 13 01 15.4 68 43 14 12 26 55.11 70 37 55.7 10 9 11 00 12 55 48.2 63 12 43 13 00 19 88 62 51 47.9 Sept. 6 9 15 01 12 57 09.7 46 18 24 12 58 58.44 43 54 44.6 Oct. 11 7 07 30 13 09 46.2 32 35 45 13 11 02.75 32 26 23.1 66 3 Hist.Cel.p. 394. B. A. C. 4614. Arg. Zone, 200. 5 Draconis. 2 3 B. A. C. 4392. July 14th. The comet was first seen at 11h. 45m. P. after watching its position for some time, we could detect no indication of motion relatively to the neighbouring stars, so that it was not recognized as a comet until six days after. Its position, as given above, was taken from the circles of the five-foot equatorial. "July 20th. The comet was observed to-night with the five-foot equatorial, using the annular micrometer for the comparisons. It disappears sharply behind the ring, with almost as much certainty as a star; indicating a sudden condensation of light at the centre. This was afterwards confirmed, on examination with the great refractor recently mounted in the dome of the Observatory. With the full aperture of fifteen inches, a very minute stellar point is visible in the centre of the comet, with a sparkling light, easily distinguishable from the diffused nebulosity which surrounds it. “July 23d. The observations were made this evening with the great equatorial, by differentiating with the hour and declination circles. In high declinations this method allows the comparisons to be oftener repeated than is otherwise practicable. In declination the comparisons have a better mutual agreement than we have been able to obtain when using the annular micrometer. "July 24th. The comet does not sensibly increase in brightness. The stellar point is visible through strong moonlight. 66 Sept. 3d. The comet still shows a star-like nucleus. A faint tail is visible, of six or eight minutes in length. "October 11th. The differences of right ascension this evening are somewhat uncertain, the altitude being too low for accurate observations. "It seems necessary to remark, that the above places of the comet given by the great refractor of Cambridge University, having been obtained in every case from instrumental readings, and not from micrometric comparisons, are not determined with the full accuracy which the instrument is capable of affording. The mode of observation has been, to bring the object, by estimation, to the centre of the field of view, marking the time, and reading the circles for each in succession, and thence deriving their relative positions; a method which, however unpromising it may at first sight appear, affords, with practice, better differences of declination than are easily obtained, with smaller instruments, by the aid of the micrometer, and in high declinations is often decidedly preferable for right-ascension differences. The right ascensions and declinations of the comet were obtained by applying the observed differences to the place of the star of comparison referred to the mean equinox of Jan. 1st, 1847. Mr. Bond presented for publication a new series of moon culminations, observed at the Cambridge Observatory during the past and present year. MOON CULMINATIONS, Observed at Cambridge, Corrected for Instrumental Errors, Clock Error, and Rate. B' is the initial of William C. Bond; B2, of G. P. Bond. |