Excerpt from Photographic Investigations of Faint Nebulae It seemed inadvisable to make an exhaustiv were to use a restricted portion of the field or to sacrifice accuracy of these evils was chosen. The positions of the optical centers of center of the field were determined empirically. Pairs of plates of 9 inches and with the full 24 inches and were compared in the Zeiss aperture, and hence the smaller focal ratio, the images near the edge small. Superimposed on the 24 inch images, they indicated where the larger distorted images. Trials were then plates, until a kind of technique was acquired. Empirical scheme fully justified itself. 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.