Royal Astronomical Society. 



307 



in the years 1832 and 1833. By Thomas Henderson, F.R.SS. 

 L. and E., Professor of Practical Astronomy in the University of 

 Edinburgh. 



This catalogue contains the right ascensions of 174 principal fixed 

 stars, reduced to January 1, 1833; being the same stars of which 

 the declinations, observed by Mr. Henderson at the Cape, are pub- 

 lished in vol. X. of the Memoirs, with the addition of ^'Eridani, 

 a Persei, and 6 Ursae Majoris. The observations of right ascension 

 (with the exception of a small number) were made by the assistant- 

 astronomer. Lieutenant William Meadows, II. N. Ithe transit in- 

 strument, by Dollond, is 9 feet 9\ inches in focal length, with an 

 object-glass of 5 inches in diameter. The magnifying powers em- 

 ployed were 88 and 132; chiefly the latter. The clock was by 

 Hardy, having one of his scapements, and a mercurial compensation 

 pendulum. During the period of the observations its rate was as 

 uniform as the rates of most transit-clocks in use at observatories. 

 The reductions of the right ascensions to January 1, 1833 (when 

 the sun's mean longitude was 281°), were computed from the tables 

 in the supplements to the Nautical Almanac for 1832 and 1833. 

 The coefl[icient of aberration was assumed to be 20'''5 ; and the 

 proper motions in right ascension were taken into account, when 

 they appeared to amount annually to O^'Ol of time. The right as- 

 censions given in the catalogue are the means of all the determina- 

 tions from observations made above and below the pole without di- 

 stinction. The annual precessions are calculated for the beginning 

 of 1833, from the Tabulae Regiomontanee. The right ascensions of 

 the present catalogue are compared with those of the same stars in 

 the catalogues of Lacaille, Bradley, Piazzi, Rumker, Johnson and 

 Pond (all reduced to the same epoch), and the differences exhibit 

 the effect of the proper motion in right ascension for each of the 

 stars respectively. 



From these differences, combined with the differences of declina- 

 tion given in Mr. Henderson's former catalogue above referred to, 

 the annual proper motions of the stars in the present catalogue are 

 obtained. A table is given, which contains such of them as appear 

 to have proper motions not less than O"* 1 of arc ; they amount to 

 35. The following are those whose annual proper motions exceed 

 0"-4. 



X2 



