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#16a.     Discovery of the Sunspot Cycle

Excerpts from Solar Observations During 1843 by Heinrich Schwabe, (Astronomische Nachrichten, vol. 20., no. 495, 1843)

The weather throughout this year was so extremely favorable that I have been able to observe the Sun clearly on 312 days; however, I counted only 34 groups of sunspots....

From my earlier observations, which I have reported every year in this journal, it appears that there is a certain periodicity in the appearance of sunspots and this theory seems more and more probable from the results of this year. ...I should like now to add a complete report of all my observations of sunspots up to the present, in which I have indicated the number of days of observation and the days when there were no spots to be seen, as well as the number of groups.

Year No. of Clusters Days when no
Spots were observed
Observation Days
1826 118 22 277
1827 161 2 273
1828 225 0 282
1829 199 0 244
1830 190 1 217
1831 149 3 239
1832 84 49 270
1833 33 139 267
1834 51 120 273
1835 173 18 244
1836 272 0 200
1837 333 0 168
1838 282 0 202
1839 162 0 205
1840 152 3 263
1841 102 15 283
1842 68 64 307
1843 34 149 324


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Author and Curator:   Dr. David P. Stern
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