Photographic Photometry Forming a Part of the Henry Draper Memorial

by Edward Skinner King

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1912 ...several groups are B4, A2, F, G, K, M. The average class of the stars actually entering into each group is given in the third column of the Table. The figure following the letter is a mean of the numbers, taken with respect to the principal letter, indicating the subdivisions to which the several stars of each group belong. The letters, a and p, have not been regarded. The fourth, fifth, and sixth columns give the sum, the mean, and the average deviation of the differences for each group. The Table shows the progressive change of the mean in the order, B, A, F, G, K, M, and indicates a corresponding change in the amount of blue or actinic light. Stars of Class B possess more actinic light than stars of Class M, the difference being nearly two magnitudes, corresponding to a ratio of about six times. The means are plotted in Figure 5, with the classes given in the third column, as abscissas. The close approximation to a straight line is remarkable. The deviations from a straight line, determined by the method of least squares and by assigning equal weights to the several groups, are given in the last column of the Table. The average deviation for the six points is 0.06 magn. The deviations for the individual stars, from the straight line thus derived, are given in the last column of Table XV. The average deviation for all the stars is 0.12 magn. This does not greatly exceed the mean of the average deviations of the individual stars from the mean of the groups, as shown in the sixth column of Table +)J0 XVI. The photographic magnitude, 2.62, was as-+u- sumed for Polaris, as stated on page 79, with the intention of making the photographic and +050 photometric scales coincide for Class A. The photometric magnitude of Polaris is 2.12. 0 Therefore...

64 pages, Paperback

Published January 1, 2012