Iwahashi Zenbei's Sunspot Drawings in 1793 in Japan

Abstract

Three Japanese sunspot drawings associated with Iwahashi Zenbei (1756-1811) are shown here from contemporary manuscripts and woodprint documents with the relevant texts. We revealed the observational date of one of the drawings to be 26 August 1793, and the overall observations lasted for over a year. Moreover, we identified the observational site for the dated drawing at Fushimi in Japan. We then compared his observations with group sunspot number and raw group count from Sunspot Index and Long-term Solar Observations (SILSO) to reveal its data context, and concluded that these drawings filled the gaps in understanding due to the fragmental sunspots observations around 1793. These drawings are important as a clue to evaluate astronomical knowledge of contemporary Japan in the late 19 th century and are valuable as a non-European observation, considering that most sunspot observations up to mid-19 th century are from Europe.

2017/11/16 accepted for publication in Solar Physics

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• Thaddäus Derfflinger's sunspot observations during 1802-1824: A primary reference to understand the Dalton Minimum
• The Solar Corona during the Total Eclipse on 16 June 1806: Graphical Evidence of the Coronal Structure during the Dalton Minimum
• Stephan Prantner's Sunspot Observations during the Dalton Minimum
• Revisiting Kunitomo's Sunspot Drawings during 1835-1836 in Japan