making a minute Survey of the Heavens. 51 



tailed than that which can be obtained by an instrument fixed 

 in the meridian. Afterwards we may propose to make on each 

 of those stars the necessary observations, in order to assign 

 more accurately its true place. 



Such then is the object of the new astronomical maps. They 

 are intended as a guide to future astronomers, whereby they 

 may know, at one view, whether there exists a star that has 

 never yet been observed. In this point of view these new maps 

 cannot by any means render superfluous the Atlas already 

 published by M. Harding, which contains all the necessary 

 details to be able to distinguish exactly in what place of the 

 heavens a comet or a new star is seen. But the different ob- 

 jects of these two maps require also a different arrangement. 

 M. Harding has taken his stars from the Histoire Celeste 

 and from other catalogues, and in the regions where the ob- 

 servations were not sufficiently numerous, he has made up the 

 deficiency as well by his own observations as by drawings. We 

 wish that, in the new maps, only those stars already observed 

 should be noted, (viz. with one or two dashes,) which are found 

 in books that are in the hands of every astronomer ; and in 

 order not to increase uselessly their number, we propose to 

 limit those books to the following ones ; 1°. The Catalogue of 

 Bradley (Bessel.Finid.Ast.); 2°. Piazzi's Catalogue (Palermo 

 1814); 3°. The Histoire Celeste of Lalande; 4°. Bessel's Zones. 

 If a star shall be found in any two of these books we may be 

 certain that it is a fixed star ; if it is found in one only, it may 

 be a planet or a moving star. It is therefore necessary that 

 every one who wishes to take a part in this plan should also 

 take upon himself to reduce, to the same epoch, the observa- 

 tions of the Histoire Celeste and of M. Bessel's Zones, in order 

 to be able to decide whether a star is either the same, or has 

 only been affected by a very remarkable proper motion. For- 

 tunately this reduction will be found neither difficult nor long, 

 by means of the Tables of Reduction that M. Schumacher has 

 caused to be computed for the Histoire Celeste*, and by the 

 help of those tables M. Bessel has adjoined to his Zones. I 

 have no hesitation to assert, by my own experience, that I 

 should be able in 8 days to compute all the necessary reduc- 

 tions for a whole hour in JR : and that at the utmost 15 days 

 would be sufficient for every case. 



M. Bessel's tables of reduction give the formula 



(1825) M = t + k + # (8 - D) x -01 

 (1825) Decl. = 8 + d + cD (8 - D) x -01 



* [Sammlung von Hiilfstafeln. Vol.ii.— Sec] 



G 2 For 



