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XXIV. On the Construction and Arrangement of the Berlin 



Astronomical Ephcmeris for 1831. By Professor Encke*. 

 npHE construction of the Epbemeris for this year is the same 

 -■- as that for the preceding one, with the exception that some 

 columns have been added to tliose relating to the positions of 

 the planets, and to the occultations of stars. With a view to 

 prevent all misunderstanding in regard to the times of rising 

 and setting of the sun and moon, and of the changes of the 

 moon, I distinctl}' remark that, with tlie exception of solar 

 eclipses, the times given never refer to apparent time, but are 

 always meant for mean solar time. 



The comparison of the end of the last with the beginning 

 of the present Ephemeris, has led to the discovery of differ- 

 ences, fortunately of no moment, which had arisen from error, 

 and from neglecting small quantities. 



In the calculation of the Ephemeris of thesun bothfor the last 

 and for the present year, the tables of Professor Bessel, pub- 

 lished, subsequently to the calculation, in Professor Schuma- 

 cher's Nachrichten, could not be applied. Having however de- 

 rived, from the corrections Wiich had been published, the ele- 

 ments on which they were founded, I constructed from the same 

 the necessary tables, and thus the difference is of any conse- 

 quence in one column onl3\ In order to obtain a rigorous 

 agreement with Professor Bessel's tables, it will be necessary 

 to increase the mean right ascension of the sun, or the sidereal 

 time at the mean noon, given in the Ephemerides for the two 

 years, throughout, by +0"'06. This correction is constant 

 through the whole year, because the smaller collections de- 

 pendent on the two nutations are exactly the same in Bessel's 

 and in my tables. 



In the calculations for the positions of the moon, my aim has 

 again been to be accurate to + 0"'5; yet there are places 

 where the differences appear to indicate the necessity of cor- 

 rections greater than this quantity. A revisal of the calcula- 

 tions having, however, not shown any error, the data have been 

 given without alteration. The columns of the place of the 

 moon at the two culminations have in the present Ephemeris 

 been calculated more accurately, and each datum has been 

 found directly without interpolation. Although the excellent 

 method of Professor Bessel of predicting occultations of stars, 

 which, with his permission, I have reprinted in this Ephemerisf, 

 will perhaps supersede the use of the lower culminations here 

 given ; yet I did not think it proper to leave them out, as they 

 were necessary to me for the calculation of occultations of 



* Translated from the original German. 



t See Phil. Mag. and Annals, Nov. and Dec. 1829. 



Stars, 



