Solar cycle
Solar cycle 16 was the sixteenth solar cycle since 1755, when extensive recording of solar sunspot activity began. The solar cycle lasted 10.1 years, beginning in August 1923 and ending in September 1933. The maximum smoothed sunspot number (SIDC formula) observed during the solar cycle was 130.2 (April 1928), and the starting minimum was 9.4. During the minimum transit from solar cycle 16 to 17, there were a total of 568 days with no sunspots.