Royal Astronomical Society. 227 



ROYAL ASTRONOMICAL SOCIETY. 



Nov. 11, 1836. — The following communications were read : — 



I. Extract from a Letter from Mr. Maclear to Captain Beaufort, 

 accompanied by the original Circle and Transit Observations of 

 Halley's Comet since January. 



The number of meridian observations thus obtained is upwards 

 of thirty. The reductions will be forwarded in a short time j the 

 delay arising from Mr. Maclear being employed in observing the 

 stars of the Brisbane list, in aid of Sir John Herschel, who, he states, 

 is now occupied in reducing his Catalogue of Southern Nebulae. 



II. A Catalogue of the Right Ascensions of 1318 Stars, observed 

 at Blackheath. By Mr. Wrottesley. 



These papers consist of a catalogue in Right Ascension of 1831 

 stars (those of the 6th and 7th magnitude inclusive, contained in 

 the Astronomical Society's Catalogue), with an explanatory intro- 

 duction and notes ; and also of the original observations, and the 

 reduced mean places, from which the catalogue is formed. As this 

 is the first contribution by a private observer to a more accurate 

 knowledge of the places of the fixed stars, which has been made in 

 consequence of the Society's Catalogue, and according to its direc- 

 tions; and as the deductions are of great value and importance ; a 

 distinct report has been made by a Committee, and adopted by the 

 Council, in order that due credit may be given to the labours of 

 Mr. Wrottesley and of his assistant Mr. Hartnup. 



The observations were made with a transit telescope, by Mr. 

 Thomas Jones, of 3J inches clear aperture, 62 inches focal length, 

 and 27 inches horizontal axis. The power used was 142. The 

 position of the instrument was ascertained, when practicable, by- 

 consecutive transits of Polaris above and below pole : and in other 

 circumstances, by single transits of Polaris or 3 Ursae Minoris. This 

 was checked, in some degree, by a close mark seen through a fixed 

 lens; which, however, discharged a better purpose in determining 

 the error of coUimation whenever the instrument was reversed. 

 This was done every month. The level was always applied (of 

 course in reversed positions) once every night, and often twice, viz. 

 at the beginning and end of a series of observations. At first, cor- 

 rections for the instrumental errors were computed and applied, 

 but the amount was found to be so small, that Mr. Wrottesley sub- 

 sequently preferred taking the clock error for the stars of his cata- 

 logue from the standard or standards, which, having nearly the 

 same declination, were affected by the same instrumental errors. 

 Thus the instrumental errors, which were always noted and kept 

 low, were, as to sense, eliminated. 



The bases of this catalogue are, the fundamental catalogue of 

 Bessel for the mean places of the standard stars (omitting some not 

 suited to Mr. Wrottesley's purposes, and substituting his own place 

 of Fomaihaut for the erroneous place of Bessel ; ) and for the correc- 

 tions, the constants and precessions of the Astronomical Society's ca- 

 talogue, and the ralues of A, B, C, D, contained in the Nautical AU 



2G2 



