Our Astronomical Column

Abstract

THE PULKOWA CATALOGUE OF 3542 STARS FOR 1855.—Dr. Backlund has given in the “Mélanges Mathématiques et Astronomiques” of the St. Petersburg Academy, tome vi., pp. 563–99, a comparison of the star places of the Pulkowa Catalogue of 3542 stars for 1855, with those of the other Pulkowa star catalogues, including the unpublished one for 1875 by Herr Romberg, as well as with the catalogues of Becker, Boss, and Resphigi. This catalogue, which forms part of vol. viii. of the Pulkowa observations, contains the mean places of 3542 stars observed with the meridian-circle of that Observatory during the years 1840–69. It includes all the Bradley stars north of S. Decl. 15°, with the exception of the Pulkowa fundamental stars, which have not been included because the catalogue-places depend on their positions as determined with the transit-instrument and vertical circle. And as the definitive positions of the present catalogue depend on the two catalogues of fundamental stars for 1845 and 1865, it appears that the system of the catalogue for the epoch 1855 will be practically identical with that of the mean of the two catalogues above mentioned. Dr. Backlund's comparisons give a very favourable view of the accuracy with which the relative positions of the stars have been determined, the probable error of an R. A. in the 1855 catalogue being ± o″.034 for a star south of N. Decl. 30°, and of a declination ± o″.30; but they also show that the problem of the determination of absolute positions is in a far less satisfactory state. A further comparison of the Pulkowa 1855 catalogue has been made by Herr Seyboth (Astr. Nach. 2808), the catalogue with which it has been compared being that of the Cape Observatory for 1880. The agreement appears to be as close as could be expected considering the unfavourable position at either Observatory of several of the stars used; the Pulkowa star places south of the equator show, however, some discordance from those obtained at the Cape as also from those of Boss's standard catalogue. From a comparison of the fundamental stars only, Herr Seyboth finds for the probable error of the Cape places ± 0.021s. in R. A., and ± 0.38s. in Decl.