The following Table shews the State of the Standard Catalogue at this present Time, Sept. 1813.* N. P. D. of Stars for the beginning of the Year 1813. The N. P. D. of Procyon in the former Catalogue was 15",03; this was from a mistake of 1",o committed in adding the annual variation, it should have been 14′′,03. * Though the Observations were given to the Society, as by the date of the paper, yet, by the permission of the President and Council, they were extended till the time that they went to the press. α Remarks on the above Observations. Lyræ and a Aquilæ having been supposed subject to a sensible parallax, I have, as I mentioned before, reserved them for future examination. The observations which I have already made on these stars, and particularly on « Aquilæ, are not incompatible with this supposition, though I cannot at present venture to decide whether the small discordances I have met with are to be attributed to any regular cause, or are only accidental. Whenever I speak of the degree of exactness to which any result may be depended upon, I allude only to the mechanical measure given by the instrument. I have every reason to believe, that if two fixed and well defined points could be placed in the plane of the meridian, I could, in a very short time, measure their angular distance to within a tenth of a second; but astronomers must be well aware that the stars are not presented to us in this simple form, and that the sources from which small errors may arise, either in the observations themselves or subsequent computation, are so very numerous, that anomalies will occur even to the most careful observer, which he will in vain endeavour to explain. With respect to the parallax of a Lyræ, I might observe that it is a star so badly defined, and so little adapted for exact observation, that a parallax of half a second would not be easy to determine even with the Greenwich circle. α a Aquila is in some respects a better star for observation, but only half its actual parallax would be sensible in declination. There are several other stars much better adapted for this investigation, even should their distance be supposed more than double, such are Polaris, ʼn Ursæ maj. « Cygni, ẞ Urs. min. and y Draconis; now in these I have not hitherto found any sensible parallax; occasional discordance has frequently suggested some slight hopes, but these have always been disappointed by continuing the observations. It is, however, useless now to anticipate this subject farther. Those stars which are in the general Catalogue, but which do not form part of the standard Catalogue, I presume to be exact to the nearest second. I have not included any star in the standard Catalogue south of the equator, on account of the uncertainty of refraction. 1813. Barometer. In. Therm. Out. Refraction. Observations as given by the Instrument. Equations for N. P. D. Equations for Zenith Distance. XXXIII. Observations of the Summer Solstice, 1813, with the Mural Circle, at the Royal Observatory. By John Pond, Esq. Astronomer Royal, F. R. S. Read July 8, 1813. Semidiameter of the by Nautical Almanack. Reduction to the Solstice. " 58,9 66 32 20,4 + 1,0 28 0 59,966 32 21,4 0,6 0,6 22,115 46,5 22 16,2 56,7 18,2+1,0 O 57-7 19,2 22, I 15 46,4 18 12,1 57,6 19,1+ 1,0| 0 58,6 20,1 22,115 46,3 14 32,4 59,6 21,1 +0,9| I 0,5 22,0 22,1 15 46,1 8 26,7 57.5 19,0 +0,7 0 58,21 19.7 22,1 15 45,8 O 1,9 I I,I 0,6 22,1 15 45,6 0 58,2 19,7 0,6 22,1 15 45,6 2 41,1 I 0,1 21,6 0,31 O 59,8 21,3 0,6 22, I 15 45,6 6 29:3 O 59.7 21,2 0,2 O 59.5 21,0 28 29,94 61 67 29 29,75 64 74 July 129,67 62 65 229,75 60 62 29,7 O UL 66 25 9,0 0,6 22,1 15 45,6| 9 0,4 I 1,8 23,3 0,1 1 1,7 23,2 30,0 LL 66 59 32,2 0,6 22,I 15 45,5 11 56,1 0 58,5 20,0 0,0 o 58,5 20,0 29,6 UL 66 35 7,1 0,6 22,1 15 45,5 19 0,7 31,8 LL 67 10 44,8 0,6 22,1 15 45,51 23 9:5 O 59,4 59,5 * Mean Obliquity at Summer Solstice, 1812 23 27 50,5 Mean of Two Observations or Mean Obliqui y, Jan. 1, 1813 23 27 50,0| * I avail myself of this opportunity of correcting a very small error that was made in computing the summer solstice of 1812. The correction for the sun's latitude should have been o",6 instead of o°,9, and should have been applied with the contrary sign. The obliquity thus corrected will be 23° 27′ 50′′,5. 28 0 59,166 32 20,6 4", Nutation 6′,5 = 10,5 10,5 10,5 28 0 48,666 32 10,1 Mean Obliquity 23 27 49.51 Solstitial Zenith Distance with Parallax. Solstitial N. P. D. with Parallax. Correction for O's Lat. Solstitial Zenith Distance corrected for O's Lat. Solstitial N. P. D. corrected for 's Lat. Nov. 5. A Description of the Collection of ancient Marbles in the British Museum with Engravings. Part I. London, 1812. DONORS. The Trustees of the British Museum. 4° A Treatise on Theatres, by George Saunders. Mr. George Saunders. The Speech of His Royal Highness the Duke of The Editor. |