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We revisit the sunspot drawings made by the Japanese astronomer KunitomoToubei during 1835-1836 and recount the sunspot group number for each image.There are two series of drawings, preliminary (P, containing 17 days withobservations) and summary (S, covering 156 days with observations), all madeusing brush and ink. S is a compilation of drawings for the period fromFebruary 1835, to March 1836. Presently, the P drawings are available only forone month, September 1835; those of other periods have presumably been lost.Another drawing (I) lets us recover the raw group count (RGC) for 25 September1836, on which the RGC has not been registered in the existing catalogs. Wealso revise the RGCs from P and S using the Zurich classification and determinethat Kunitomo's results tend to yield smaller RGCs than those of othercontemporary observers. In addition, we find that Kunitomo's RGCs and spotareas have a correlation (0.71) that is not very different from thecontemporary observer Schwabe (0.82). Although Kunitomo's spot areas are muchlarger than those determined by Schwabe due to skill and instrumentlimitations, Kunitomo at least captured the growing trend of the spot activityin the early phase of the Solar Cycle 8. We also determine the solar rotationaxis to estimate the accurate position (latitude and longitude) of the sunspotgroups in Kunitomo's drawings.

Revisiting Kunitomo's Sunspot Drawings during 1835-1836 in Japan