  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.
