178 



On the Construction a?id Arrangement 



manner of calculating the reductions. Neither can it be de- 

 nied that for well-furnished observatories too great a number 

 of principal stars is unnecessary and a waste of time. I have, 

 however, believed, that I ought not to swerve from the example 

 of Professor Schumacher. For observatories which have not 

 the advantage of a perfectly firm position of their instruments, 

 a greater number of northern stars, which may be observed 

 both above and below the pole, may be of advantage in many 

 cases, even if the rigorous determination may be better de- 

 rived from the thirty-six principal stars. Some differences, 

 imperceptible in practice in the mean places, compared with 

 the data of the preceding year, arise from a new derivation ot 

 the same. 



New tables of 8 Ursae Minoris, which we are to expect from 

 Professor Bessel, could not yet be made available for the pre- 

 sent year. A comparison of these tables with the data for 1830 

 and 1831, has proved that the following corrections are to be 

 applied to the date of the Ephemeris with respect to this star. 



Applying therefore, in both Ephenierides throughout, these 

 corrections, — 



Right ascension +0"-G0 (time) 



Declination +0"-24 (arc), 



we shall have nearly such an approximation to the latest de- 

 terminations, as a rigorous calculation by them would have 

 admitted. 



Agreeably to the wish of some of the astronomers who use 

 this Ephemeris, I have given the conjunction of the planets 

 Mercury, Venus, Mars, Jupiter and Saturn, with the moon 

 and with each other, in every case in right ascension, for every 

 month, even when no occultation will take place. For the 

 four new planets the intensity of light in their opposition has 

 been given agreeably to Professor Bessel's idea ; viz. that the 

 intensity of light which the planet would have when equi- 

 distant 



