Observations of the solar surface were commenced by the writer in August, 1890, and brief reviews have been published in these Proceedings from time to time, the first being in Volume X, 1902, and succeeding ones in Volume XV, 1908, and Volume XXVIII, 1921, the present paper brings the series down to the close of the year 1925, covering a period of over 35 years and embracing four minimum and three maximum epochs of the 11½ year cycles of solar changes. All of the five years' observations were made with a 5½-inch refracting telescope, equatorially mounted, being the same instrument which has been in use since September, 1907.
Proceedings of the Iowa Academy of Science
©1926 Iowa Academy of Science, Inc.
Hadden, David E.
"The Solar Surface during the past Five Years a Review of Sunspot Observations Made at Alta Iowa from 1921 to 1925,"
Proceedings of the Iowa Academy of Science, 33(1), 225-229.
Available at: https://scholarworks.uni.edu/pias/vol33/iss1/50