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arXiv · 2606.24321

Chinese Sunspot Drawings and Their Digitization-(VIII) Release of a Machine Readable Parameters Catalog

G. H. Lin·S. Liu
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Abstract

We present a systematically revised and manually verified digital catalog of historical sunspot drawing observations from Chinese observatories, encompassing sunspot number, sunspot group number, and sunspot area measurements. This represents an updated release of China's early sunspot drawings that have been utilized in numerous published studies over the years, with ongoing refinements and corrections progressively incorporated during the course of those studies and now consolidated through a systematic round of data revision aimed at improving internal consistency and usability for the broader research community. To facilitate scientific utilization, selected comparisons with international reference sunspot data are presented, focusing on relative sunspot numbers (RSN) and sunspot group numbers (GN) from Yunnan Observatory (YNO) and Purple Mountain Observatory (PMO), while sunspot area measurements are also included in this release but are not compared with international datasets in the present work. For RSN, both raw and k-corrected values are analyzed; for GN, only raw counts are used as no dedicated correction factor exists in the Chinese records. The results demonstrate strong positive correlations, with correlation coefficients consistently exceeding 0.95 for all comparisons, confirming the reliability and scientific value of these historical records. Systematic differences are observed: raw YNO RSN values are systematically higher than SIDC by about 17.6\%, while raw PMO RSN values are about 6.0\% lower. After k-correction, YNO shifts to a 20.9\% deficit, suggesting over-correction, while PMO remains lower with a 15.5\% deficit. Notably, GN exhibits smaller systematic offsets (16.5\% for YNO and 8.5\% for PMO) and serves as a more robust index for long-term solar cycle studies.

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G. H. Lin, S. Liu. 2026-06-23. Chinese Sunspot Drawings and Their Digitization-(VIII) Release of a Machine Readable Parameters Catalog. https://arxiv.org/abs/2606.24321

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