THE 



PHILOSOPHICAL MAGAZINE 



AND 



ANNALS OF PHILOSOPHY. 



[NEW SERIES.] 



FEBRUARY 1827. 



XX. On some nexo auxilim-y Tables for determining the ap- 

 parent Places of the Greenwich Stars. By Francis Baily, 

 Esq. F.R.S. L.S. and G.S. and M.R.I.A. 



To Mr. Taylor. 

 1. TN a late Number of your valuable Journal*, you have 

 -'- noticed the Nevo Tables for facilitating the computation of 

 Precession, Aberration arid Nutation recently published by the 

 Astronomical Society of London. These tables certainly pre- 

 sent the most convenient mode of computing those quantities, 

 when occasionally required : but they, by no means, supersede 

 the utility and (in the present state of astronomy, I may say) 

 the necessity of those Special Tables for the daily corrections 

 of the Greenwich stars, which were computed also at the ex- 

 pense of the Astronomical Society, at the suggestion (I believe) 

 of Mr. Herschel ; and who has written an excellent Introduc- 

 tion to the same. 



2. It is well known that Mr. Herschel's tables are intended 

 only to be siibsidiary to the formation of other tables of the 

 corrections which are daily required in an active observatory : 

 and to save the time and labour which must otherwise be em- 

 ployed in determining those quantities. And, in the compu- 

 tation of those daily values, it will be evident to the experi- 

 enced calculator that a still greater saving of time and labour 

 might be effected if the computations of one year could be 

 made subservient to those of the following years. This may 

 be readily done with respect to the aberration: since the place 

 of the sun on any given day will never differ more than 15 or 

 16 minutes from its place on the same day in any contiguous 

 year : and by a previous arrangement of the tables, the cor- 



* Phil. Mag. Nov. 1820. 

 Neiv Scries. Vol. 1 . No. 2. Feb. 1 827. M rection 



