A Catalogue of the Magnitudes of 1081 Stars

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Excerpt from A Catalogue of the Magnitudes of 1081 Stars: Lying Between -30° Decl, And the South Pole, From Observations Made in the Years 1885-6 The observations on which the present Catalogue is based were made in the course of a voyage to Australia, round the Cape of Good Hope, and back by the Red Sea, including a stay of two months in Australia. The following is an account of the manner in which the observations were made. Before leaving England seven groups of comparison stars were selected from "Harvard Photometry" and several hundred observations of the brightness of stars north of south declination 30° were made in the same manner as is described farther on, in order to acquire practice in the work. The star atlas made use of throughout was Proctors smaller Star Atlas, with the addition of all the other stars contained in the large maps published by the Society for Diffusing Useful Knowledge. Nearly all the stars contained in Lacaille's original Catalogue of 1942 stars and lying south of -30° declination were thus included. All the stars observed have been identified by comparison with the maps of the "Uranometria Argentina, " with the exception of a few stars not contained in that work. The observations were made by means of an opera-glass accurately focussed. The star undergoing observation was first brought into the centre of the field, and as soon as a satisfactory impression of its brightness had been received, comparison was made as quickly as possible with, usually, two comparison stars, one being a little brighter and the other a little fainter than the star observed. The star undergoing observation was then again brought into the field of the opera-glass and compared with the impression which had been received of the brightness of the comparison stars. This operation was generally repeated several times, until a perfectly satisfactory estimate of the brightness of the star relative to the comparison stars had been obtained, when the result was recorded. The adopted magnitudes of the comparison stars being known, the interval between any two of them was mentally divided into as many parts as there were tenths of a magnitude between them. By this means the value of a step was made to correspond with a tenth of a magnitude on the scale of the "Harvard Photometry." About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.