250 



Mr. Groombi'idfje o}i his Tables 



out of the Nautical Almanack the longitude of the eaFth (allow- 

 ing for the constant of aberration 20", and also the lunar 

 equation contained in the longitude of the sun), and the di- 

 stance of the sun ; proceed direct to the right ascension and 

 declination of the planet These latter for the ephemeris at 

 midnight may be easily found by interpolation. 



The following are two observations of Vesta, made on the 

 meridian, which happen to be convenient to find the apparent 

 opposition of the planet. 

 I82iJ. Meantime. ^. Dec. S. Long. , Lat. N. 



I "• / // o I II o I II o I II \ O I ll 



June 14 12 8 3-4 264 43 42-6 18 57 21-3 263 0-6 4 2o 9-4 

 17 I 11 53 11-3 [263 57 28-8 19 8 31-1264 16 39-7| 4 12 lff-9 



I have assumed — 7"'2 for the parallax in declination, and 

 23** 27' 53"-0 for the apparent obliquity of the ecliptic; 

 whence the above will be found the geocentric longitude and 

 latitude: the opposition appears to be, on June 15th, at 22'' 

 48' 59-"2 mean time, in longitude 264° 39' 3"-4; latitude 

 N. 4° 18' 53"-8. Applying 9' 20", for the difference of the 

 meridians of Paris and Blackheath, will show the opposition 

 to have taken place at Paris on June 15th, 22'' 58' 19", being 

 4' 50'' later than the time given by Professor Encke. 



Tlieyc different results will appear in the following com- 

 parison ; 



Paris. Blackheath. 



] 

 Appaieiit opposition, M.T., June 15th 



True longitude .. ... .. 



Computed longitude 



Error ... 

 True latitude North ... 



Heliocentric latitude 

 Computed heliocentric latitude . . . 



Error . . . 

 It therefore appears that I had supjiosed the mean longi- 

 tude of the orbit about 3' in excess. The Ephemeris of Pro- 

 fessor Encke gives a mean error in JR — 2' 36"*7, and in Dec. 

 -f 14"-5: my Ephemeris gives an error in ^ + 3' 16"'5, and 

 in Dec. +^"'1. The difference in the time of opposition may 

 arise from the use of. different reductions of the earth's longi- 

 tude ; yet the Connaissancc des Terns, preceding the Nautical 

 Almanack 22" in the longitude of the sun, being equal to the 

 distance of the meridians of Paris and Greenwich, should not 

 affect the deduction. The difference 13"*7 in the true geo- 

 centric latitude of the planet, will partly arise from the later 

 is to be found in the principle of attraction, which, being a 

 power inherent in matter, effects all motion, from that of the 



sDJallest 



